Review of seed systems for bananas and plantains (Musa spp.)
By Kim S. Jacobsen
This paper was prepared under contract with Bioversity International for the Roots, Tubers & Bananas (RTB)
project ‘Farmer access to banana quality planting material - a review of relevant socio-economic and
biological factors’ & the RTB project ‘Developing tools for describing, quantifying and managing diseases
causing degeneration of planting material in RTB’.
The positions and opinions presented are those of the author alone and are not intended to represent those
of Bioversity International.
1
Executive Summary
Musa spp. are grown in nearly 130 countries throughout the tropics and subtropics, 85% of
production is by small-scale farmers for home consumption or for sale in local and national
markets, providing a staple for over 400 million people. Despite the importance of this crop,
activities in the Musa seed system remain largely uncoordinated and, in many countries, R&D
and regulatory capacity is unable to implement the strategic framework necessary to ensure the
quality of planting materials.
Traditional Musa planting material consists of suckers, which are detached from the mother plant
and transplanted elsewhere, shared or sold. In small-scale Musa farming systems, a prevalence
of pests and diseases is frequently combined with a general lack of knowledge of management
options. This results in the transmission of many infections through infested suckers. The most
important seed borne pests and diseases for Musa planting materials are nematodes, weevils,
Fusarium wilt (race 4), and viruses including Banana Bunchy Top Virus (BBTV), Banana Streak
Virus (BSV), and bacterial wilts. Nematodes and weevils can be managed fairly simply on-farm.
The ideal management of the diseases affecting Musa planting materials is through tissue-culture
technology. In the face of high threat diseases, such as Foc TR4, BBTV and bacterial wilts, the
imperative for efficient low-cost rapid multiplication technologies is clear. Large-scale
multiplication of a few selected cultivars poorly accommodates the cultivar diversity observed in
many Musa farming systems.
The establishment of certified mother plant gardens to preserve local genetic resources and
serve as a source of virus-free and true-to-type mother plants has been suggested (Dubois et al.,
2013 – in press). Care should be taken to locate such gardens in localities representative of the
most frequently occurring soil and climatic conditions. Where local diversity is less pronounced,
importation of additional cultivars might be warranted as a source of resistance to pests and
diseases. Virus testing at such mother-plant gardens may be coupled to give support to local
quarantine services. The use of horticultural techniques, such as macropropagation in
combination with ELISA testing, may prove a practical solution to multiply planting materials while
avoiding the steep investment required for tissue-culture facilities. Pilot tests are currently
underway.
Re-infestation jeopardizes the benefits associated with the use of clean planting materials.
Additional studies are needed to clarify the biological mechanisms and parameters associated
with re-infestation of clean planting materials, and to identify latency periods for Musa pests and
diseases. This would help to determine delimitation requirements of quarantine zones, as well as
providing useful information for farmers planning a new field or plantation expansion.
Experimental data is needed to quantify the relationship between sanitary quality and
multiplication method. Likewise, the potential yield associated with tolerance levels should be
determined for buyers (and sellers) to evaluate the relative importance of non-compliance with
quality standards for planting materials.
Considering the BSV activation risks associated with tissue-culture propagation of AAB cultivars,
more research is needed in order to define appropriate protocols for the safe movement of AAB
germplasm.
It is unclear how the term “degeneration” applies to Musa spp.
Technologies to clean conventional suckers were published over 50 years ago and technologies
to multiply high quality planting materials have been known for at least 20 years. Recent efforts
have been made to consolidate this information into practical illustrated guidelines (Lescot and
Staver, 2010; Staver and Lescot, 2013). Numerous national, bi- or multilaterally funded projects
have targeted improvements for Musa seed systems through public-NGO partnerships,
sometimes with private sector involvement. Yet, the adoption of improved planting materials,
particularly by small-scale farmers, remains marginal at best.
In many Musa producing countries, R&D and regulatory services are unable to ensure the quality
of planting materials. So, despite the availability of a potential solution, a lack of high quality
planting materials continues to be identified, in rural appraisals and country reports, as a major
constraint for the sustainable intensification of Musa production.
Adoption of multiplication technologies by medium- and large-scale market-oriented farmers in
demand-driven scenarios has been fairly successful. Small-scale farmers, by contrast, have
generally been exposed to multiplication technologies in a supply-driven scenario (e.g. the NGOand government-sponsored donations, subsidized, or micro-credit mediated technology transfer
2
projects). Many of these technology transfer initiatives would benefit from a rigorous analysis of
the socio-economic benefits and evaluation of the criteria that foster adoption, before scaling up
dissemination efforts.
There is a need to develop adequate certification schemes that are able to operate under
resource-poor conditions. Farmers have shown willingness to invest in improved planting
materials, but the inability to provide guarantees towards genetic and sanitary quality greatly
hamper optimal technology transfer.
Several national strategies exist for the provision and/or certification of Musa planting material, as
well as regulations on an international level. Regional strategies are poorly developed.
Quarantine officers from countries lacking experience may benefit from training provided by
quarantine officers from more experienced countries. Development of online infrastructures (e.g.
coupling CABI Crop Protection Compendium to proMusa specialist services?) and regional hubs
for information relevant to Musa quarantine services could provide additional support with minimal
investment.
In many Musa producing countries a more accessible and reliable information network would
benefit both the capacity of national quarantine services, especially remotely stationed duty posts,
and help to develop a market for traditional or improved planting materials. Numerous reports can
be found of mobile phone initiatives tailored to the needs of farming households (UNCTAD,
2010). Exploitation of mobile phone networks and rural radio services in resource poor settings
may assist fast and reliable information transfer for isolated locations. Locating buyers and sellers
of Musa planting materials may thus be facilitated using mobile phone technology. Mobile phones
may also provide quality certificates for in-country or regional germplasm transfer. This would
allow national services to quickly map national and regional germplasm transfer networks and
allow better-targeted future interventions.
This paper discusses the availability, accessibility and quality of planting materials for farmers of
bananas and plantains (Musa spp.), following a review of published and grey literature on Musa
seed systems. It includes an overview of the research related to Musa planting materials and the
main topics touched by the literature (section I). The following sections focus on the genetic,
sanitary and physiological quality aspects of Musa planting materials (sections II-IV) and a
summary of the key multiplication technologies (section V). The second part of the review
discusses farmer knowledge and practices for the management of Musa planting materials,
socioeconomic factors related specifically to access to planting materials among smallholders,
and institutional factors related to Musa planting materials. Specific attention is given to the
linkage between public and private stakeholders with the informal system, and gaps in the
literature (sections VI – IX). In the conclusion, integrated perspectives on challenges and
opportunities for small farmer access to improved Musa planting materials are discussed (section
X).
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Table of contents (highlights = elements related to seed “degeneration”)
Executive Summary ..........................................................................................................................2
I.
Introduction ............................................................................................................................5
a. Brief overview on research related to Musa planting materials and main topics touched
by the literature. .......................................................................................................................5
b. Main characteristics of the crop, including genetic diversity, in relation to the use and
management of planting materials ...........................................................................................6
c.
Strategic first reflections: ..................................................................................................7
II.
Genetic factors related to Musa planting materials..............................................................8
III.
Physiological factors related to Musa planting materials ...................................................9
a.
Quality issues related to the crop growth cycle, sucker size and physiological state ......9
b. Climatic conditions, volume and quality of the planting materials, main abiotic
constraints that influence sucker production (frosts, floods, drought, etc) ..............................9
c.
IV.
Sucker uniformity and batch size in Musa planting material quality .............................. 10
Sanitary factors related to Musa planting materials ........................................................ 11
a.
Main seed-borne diseases of Musa planting materials ................................................. 11
b.
Main pests that influence seed production or availability .............................................. 16
Available technologies for multiplication – rates, time, costs, infrastructure requirements
18
V.
a.
Suckers extracted from a field in production ................................................................. 18
b.
Suckers produced in field multiplication plots ............................................................... 19
c.
Detached corm techniques ............................................................................................ 19
VI.
Farmer knowledge and practices for management of Musa planting materials ............. 21
a. Description of the main traditional practices of seed management by farmers, including
maintenance of genetic diversity........................................................................................... 21
b. Factors influencing the quality of Musa planting materials and access to improved
planting material among poor households ............................................................................ 22
c. Factors influencing quality of Musa planting materials and access to improved planting
material influenced by gender ............................................................................................... 24
VII.
Socioeconomic factors related specifically to access to planting materials among small
holders ....................................................................................................................................... 25
a.
Supply and demand studies .......................................................................................... 25
b.
Returns to investment ................................................................................................... 30
VIII.
Institutional factors ....................................................................................................... 33
a.
Policies and regulations related to seed ........................................................................ 33
b.
Public and Private stakeholders, partnerships and linkage with the informal system... 36
IX.
Gaps in the literature ....................................................................................................... 40
X. Conclusions and integrated perspectives on challenges and opportunities for small farmer
access to improved Musa planting materials ............................................................................ 41
XI.
References ...................................................................................................................... 45
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Grey = needs input
I.
Introduction
Bananas and plantains are currently found in all regions of the world where conditions are
suitable for cultivation. Despite the bulky and perishable nature of Musa1 suckers, together
with humans, the crop traversed oceans and colonized distant shores. Musa spp. are one of
the oldest cultivated plants in the tropics, thought to have been domesticated in Papua New
Guinea 10 000 years ago (Denham et al., 2004). Strict vegetative propagation (i.e., cloning)
over long periods of the most popular seedless diploid and triploid varieties led to somaclonal
variants, thus amplifying phenotypic diversity. The centre of origin of the wild bananas
stretches from India to Melanesia and from Nepal to Papua New Guinea (De Langhe, 1996;
De Langhe et al., 2009). A second, large diversification took place for plantain cultivars in
Central Africa, from southeastern Nigeria to Gabon (Mbida et al., 2001; Blench, 2009) and for
East African highland banana cultivars in East Africa (De Langhe, 1996). It has been
suggested that agriculture in Central Africa may have developed based on plantains (Mbida
et al., 2004) and that plantains assisted the Bantu expansion, by serving as a high-yielding
staple that could be successfully grown in the tropical rainforest (Blench, 2009).
a. Brief overview on research related to Musa planting materials and main topics
touched by the literature.
Traditional Musa planting material consists of suckers, which are detached from the
mother plant and transplanted elsewhere, shared or sold. In small-scale agricultural
farming systems the prevalence of pests and diseases is often combined with a
general lack of knowledge of management options and many seed-borne infections
are transmitted through infested suckers. Production losses due to pest and disease
build-up are exacerbated by the relatively long growth cycle of Musa cultivars,
leading to an increased risk of yield loss and eventually, plantation decline (Danso et
al., 1999; Schill et al., 2000; Holderness et al., 2000; Blomme et al., 2012). Where
Musa spp. are able to benefit from household refuse or generous mulching, perennial
production has been observed. More often, however, soil fertility issues reduce crop
longevity and, particularly under intensive management regimes, banana yields tend
to fall from three to five years after planting, declining rapidly after ten to fifteen years.
Plantain yields will decline at an even faster rate. For existing yields to be maintained,
a cyclical process of replacement of old for new plants must be undertaken (Arias et
al., 2003; Wilson et al., 1987a).
Musa planting materials are predominantly produced, selected and stored by
farmers, particularly in developing countries. This so-called informal seed system2
(also called local or farmers’ seed system) is usually defined as the total of seed
production activities of farmers (Almekinders, 2000; Singh et al., 2011). The formal
seed system, by contrast, is purposively composed of separate activities to provide
new varieties, maintain their purity and distribute them, with much involvement by the
public sector, usually via an inspection process known as “certification” (Almekinders,
2000; Thiele, 1999; Bentley et al., 2011).
For Musa, highly variable conditions can be found for the procurement, production
and trade in planting materials – between commercial or subsistence systems,
between more traditional or more industrial farming systems and between regions
where Musa spp. play a more or less important role for household income and food
security. Musa spp. are grown in nearly 130 countries throughout the tropics and
1
Bananas and plantains will alternately be referred to as Musa spp, and where used as an adjective, they may be referred
to simply as Musa (i.e. Musa cultivation).
2
The informal seed system (also called local or farmers’ seed system) is usually defined as the total of seed production
activities of farmers, mostly small-scale farmers. Seed production in the informal system is most often incorporated in the
normal crop production and represents the basic components of crop development and variety maintenance
(Almekinders, 2000).
5
subtropics, 85% of production is by small-scale farmers for home consumption or for
sale in local and national markets, providing a staple for over 400 million people.
Despite the importance of this crop, activities in the Musa seed system remain largely
uncoordinated. In many countries, R&D and regulatory capacity is unable to
implement the strategic framework that is required to ensure the quality of planting
materials (see also Lescot and Staver, 2010; Staver et al., 2010; Nweke et al., 2011).
For farmers cultivating an existing plantation, sucker production is usually adequate
and sustainable, allowing a continuous availability of planting materials of sufficiently
high quality. Yet, a lack of high quality planting materials has consistently been
identified in rural appraisals and country reports as a major constraint, hampering a
sustainable intensification of Musa production (Ndubizu, 1979; Baiyeri and Ajayi,
2000; Setyobudi, 2000; Oliveira de Almeida et al., 2000; Dankyi et al., 2007;
Tomekpe et al., 2011). In fact, a lack of planting materials only becomes critical under
certain conditions. For example, for farmers a higher need for suckers may arise
when (1) expansion needs to meet newly emerging market opportunities or (2)
sanitary constraints or disasters decimate on-farm capacity to replace infected or
destroyed mats with new suckers. For NGOs and research institutes, an increased
need for planting materials may arise where (1) large-scale dissemination of elite
cultivars and hybrids is envisioned or (2) planting materials are needed for the set-up
of field trials for research or demonstration.
Since the early 90s, most larger banana plantations have adopted micropropagation 1
as a preferred technology for the mass production of quality planting materials (Arias
et al., 2003). Macropropagation techniques were developed in the late 1990s (Munoz
and Vargaz, 1996; Auboiron, 1997; Kwa 1997). In Latin America some intensive
plantain plantations have adopted macropropagation techniques to allow high density
planting, although the use of microcorms in combination with field multiplication
techniques is more widespread (Rosales et al., 2010; Staver, personal
communication). Wide scale adoption of these multiplication technologies has not
followed, however, particularly at the level of small-scale farmers. Likewise, the use
of paring in combination with thermotherapy to clean suckers from seed-borne pests
and diseases has been known for more than 50 years (Colbran, 1967), yet
application remains marginal at farm level, especially in developing countries.
b. Main characteristics of the crop, including genetic diversity, in relation to the
use and management of planting materials
Musa plants are vegetatively propagated through lateral shoots originating from the
corm or true underground stem of the mother plant (Figure 1). Sucker development
consists of three distinct stages: peeper, sword and maiden suckers. Young shoots
only just emerging through the soil surface are termed peeper suckers. As peeper
suckers grow, they may develop lanceolate leaves and a large corm (sword suckers),
or they may develop as water suckers which have a narrow pseudostem, broad
leaves and small corm. Sword suckers and the more mature maiden suckers, are the
preferred planting material (Swennen and Ortiz, 1997; Robinson, 1995). Horizontal
growth of the belowground plant is slight, each shoot turning up to form a new aerial
stem as soon as it is clear of the mother plant, thus forming mats, which is the clump
of plants originating from a single mother plant. The largest following sucker, or
selected sucker, is termed the ratoon sucker and produces the bunch of the second
growth cycle or first ratoon (Simmonds, 1966). The apical meristem, located on the
apex of the corm, forms the leaves and will eventually produce the inflorescence
(Price, 1995). After flowering, no new roots are formed, however, they may continue
to provide nutrients for sucker development well after harvest (Blomme et al., 2002).
1
Micropropagation is a synonym for tissue culture or in vitro. Planting materials derived from this technique are termed
plantlets.
6
Figure 1: Musa planting material: sucker types (Swennen and Ortiz, 1997)
Musa planting material is defined by its physiological, genetic and sanitary qualities.
In other words, a batch of high quality planting material should contain high-yielding
suckers or plantlets of the desired cultivar(s) without pests or diseases.
c. Strategic first reflections – these need some re-thinking and discussion:
Main challenges are situated in the following themes:
i. Seed Multiplication/Availability: key challenges/opportunities for
making seed (planting material) available on sustainable basis (top
three issues?)
1. Macro- and micro-propagation plantlets for production
requires significant knowhow and investment, under what
conditions will efforts to transfer the technology be most
efficient? How can we overcome constraints in the adoption
of multiplication strategies and use of plantlets?
2. How can we develop more efficient low cost rapid
multiplication for local seed systems to benefit poor rural
households and rural women, particularly with regard to
high threat diseases (BBTV, Foc TR4, bacterial wilts)?
3. How to conserve cultivar diversity through use? How can
we incorporate cultivar diversity in mass propagation
schemes?
ii. Seed Delivery/Dissemination: key challenges/opportunities for
setting up sustainable delivery systems (top three issues?)
1. What procedures should be developed to allow movement
of plantain germplasm with minimal risk from BSV
2. How to develop quality control standards and strategies to
ensure their implementation at a national/regional level?
What role can existing international standards play?
3. What farmer training approaches will help to increase the
contribution of planting material to crop productivity and
value?
7
II.
Genetic factors related to Musa planting materials
Study of the repeatability of phenological traits, shows that botanical features used
for the morpho-taxonomic classification of plants, such as plant height, number of
leaves and number of fruits per bunch, are fairly stable. These traits exhibit minimal
non-hereditary variation, as they are controlled by a limited number of genes (Ortiz,
2000). Traits affected by the crop cycle, such as days to flowering and fruit filling
time, have much lower repeatability. Likewise traits affected by abiotic and biotic
constraints, such as fruit maturity, bunch size and weight, are also more variable
(Tenkouano et al., 2012)1.
For example, due to the apical dominance of the meristem in plantains, bananas
generally have better suckering growth than plantains and sourcing sufficient planting
materials is generally a bigger constraint for plantain cultivars (Swennen, 1984; Ortiz
and Vuylsteke, 1998). Apical dominance is a trait that will not vary from one
generation to the next. However, a physiological study of suckering behaviour
showed that gibberellic acid and cytokinin play a key role in suckering. And, since
both phytoregulators are formed in root tips, it follows that factors that stimulate root
branching, such as soil fertility and mulching, will have a beneficial effect on the
number of suckers produced (Swennen, 1984).
Cultivar-related susceptibility to adverse conditions will also impact the quality and
availability of Musa planting materials. For example: comparative to bananas,
plantains are generally more susceptible to nematode attack (Price, 1994; Fogain
and Gowen, 1998), weevil attack (Ortiz et al., 1995; Pavis and Lemaire, 1996;
Messiaen, 2002) and poor soil fertility (Wilson et al., 1987a; Swennen et al., 1988).
Genetic changes can occur during the process of micropropagation. Many of these
changes are hereditary in nature, and therefore transferrable to future generations.
This phenomenon is called somaclonal variation and care is needed during
multiplication to reduce the incidence to an acceptable level (<3%) (Smith, 1988).
This process has been observed in the following characteristics: stature (dwarfism,
gigantism), foliage (narrow drooping leaves, waxiness, variegated leaves etc),
pseudostem (purple-black or greenish colorations), bunch (hairy fruit, narrow
elongated male bud, small bunches etc); of which dwarfism is by far the most
common (Larkin and Scowcroft, 1981; Scowcroft, 1984; Smith, 1988). Genotypespecific variability in the % off-types produced has also been documented. For
example, an intensive survey of off-types present in ‘Grande Naine’ and ‘Saba’ tissue
cultured plantlets, demonstrated significant percentages of off-types for the AAA
‘Grande Naine’ (6-10% off-types by 6 months after planting and a total of 25% off
types by flowering), but no off-types for the Saba cultivar, which has an ABB or BBB
genome (Stover, 1987). Micro- and macropropagation multiplication rates are also
influenced by genotype and thus variable among cultivars (Hirimburegama and
Gamage, 1997; Baiyeri and Aba, 2005). Genotype also has an influence on the
variation of survival of macropropagated plantlets, rooting, days to emergence of
plantlets and response to weaning/rooting media. Survival rates for macropropagated
plants are generally higher for landraces, compared to hybrids (Baiyeri and Aba,
2005).
The presence of Banana Streak Virus (BSV) endogenous pararetrovirus (EPRV) in
the genome of interspecific triploid (AAB) and tetraploid (AAAB) varieties results in
restricting the use of micropropagation. The tissue culture process itself is suspected
of activating BSV EPRVs in virus-free shoot tips, especially in plantain cultivars, thus
severely limiting available options for international exchange. Other varieties,
especially those with the Musa acuminata genome, present no risk of BSV EPRV
activation during tissue culture (Lescot and Staver, 2010).
Results from a meta-analysis of datasets from previous IITA Musa multi-environment trials. The study aimed to define
the optimum plot configuration for Musa field-testing based on the repeatability of yield and phenological characteristics
across and within locations in West Africa. These trials included a sample of plantain–banana hybrids, African plantain
landraces, exotic, cooking and dessert banana cultivars and diploid parental banana accessions (Tenkouano et al., 2012).
1
8
The systematic selection of suckers from more vigorous mother plants can lead to a
more vigorous crop, resulting in improved crop productivity. In a six-year study of
crop productivity of tissue-culture derived plants, Khayat et al. (2004) systematically
selected clones using the criterium “yield per mat” (calculated as the sum of all
bunches). The best clones were again multiplied using tissue culture. The yield of
these ‘superior’ clones was then compared to that obtained from those that had
produced an average yield. The number of bunches per mat, average bunch weight
and total yield per ha were significantly higher than the mean values for the total
population (Khayat et al., 2004).
Somaclonal variation of tissue cultured plants has been successfully exploited in
Taiwan since 1983 as a means to select derived banana varieties with desirable
agronomic traits such as shorter plant height, bigger bunches, shorter maturing, and
most importantly, resistance to Fusarium wilt race 4 (Singh et al., 2011). By contrast,
somaclonal variation through micropropagation is of limited use in plantain
improvement as it mostly mimics naturally occurring variation along with the observed
poor horticultural performance of somaclonal variants (Vuylsteke et al., 1996).
Selection for improvement of the genetic stock of existing varieties by searching for
mutations can be accomplished only infrequently, because mutation has a frequency
of occurrence of only 1/500 000 plants (according to Simmonds, 1962 in
Johannessen, 1970).
III.
Physiological factors related to Musa planting materials
a. Quality issues related to the crop growth cycle, sucker size and physiological
state
Sword suckers with a large or medium-size corm are the preferred planting material.
Large water suckers will also perform well and trials with plantain have shown that
water suckers can result in an equally productive crop if given proper care when
young. Selection of small water suckers, as opposed to sword suckers, will result in
lower vigor, lengthening of the growth cycle and lower yield in terms of weight and
number of marketable fruits per ha (Rodriguez and Irizarry, 1979; Belalcazar, 1991).
Vigorous vegetative plant growth is generally associated with earlier flowering and
heavier bunch weights (Swennen and De Langhe, 1985).
Plantlets derived from microcorms, macro- and micropropagation must be processed
in hardening nurseries. This phase is intended to bring the plantlets to the stage
where they are ready to be planted in the field. Properly hardened plants are ready
for transplanting when the last fully emerged leaf measures 20–30 cm in length. No
off-type plants should be present and the plants should be of one variety only (Lescot
and Staver, 2010).
The planting material should have the uniformity appropriate for the objectives and
resources of the grower: high uniformity where a smaller market window is targeted
and less uniformity when preference is given to a longer harvesting period, as is often
the case for home consumption (Lescot and Staver, 2010).
b. Climatic conditions, volume and quality of the planting materials, main abiotic
constraints that influence sucker production (frosts, floods, drought, etc)
An inevitable challenge when discussing the quality of Musa planting materials, is the
fact that no matter how clean the material is at planting, the advantage it provides, is
only as good as the soil it is planted into. For example, the use of clean planting
material, in the form of hot-water or boiling-water treated suckers (Colbran, 1967;
Hauser, 2007), macro- or micropropagated plantlets, is often advocated to reduce
nematode-related damage to bananas and plantains (Tenkouano et al., 2006). It has
been demonstrated that the efficacy of this practice is severely reduced when clean
planting material is (inter)planted into a nematode-infested field (Speijer et al., 2000;
Speijer et al., 2001b; Elsen et al., 2004; Jacobsen, 2010).
Plantlets from microcorms, macro- and micropropagation will generally require
additional care at planting, as the more fragile root systems are more susceptible to
9
pests, diseases and adverse climatic conditions (Vuylsteke and Ortiz, 1996; De
Waele et al., 1998; Blomme et al., 2000). For example, failure to irrigate micro- and
macropropagated plants during the dry season, can lead to more than 50% losses
(Mekoa and Hauser, 2010). The inoculation of plantlets with fungal endophytes can
reduce plant susceptibility to pests and diseases, thus extending the benefits of clean
planting material (Dubois et al., 2006). Single species endophyte inoculations seldom
achieve control levels as high as those observed in greenhouse and field trials.
Recent studies suggest that the use of a cocktail of antagonistic endophytes may
enable long-term nematode control (Sikora et al., 2010).
c. Sucker uniformity and batch size in Musa planting material quality
Genetic uniformity of the batch of suckers (or plantlets) is important with regards to
agronomic and economic management. Suckers are best selected by examining the
mother plant for desired characteristics, as it is impossible to ascertain the genetic
quality of Musa suckers once they have been detached from the mother plant.
Batch heterogeneity may lead to the production of bunches of less marketable
varieties and heterogeneity may also result in variable cultivar-related susceptibility to
biotic and abiotic constraints, resulting in possible loss of productivity and yield. Giant
cultivars might be more susceptible to toppling, if planted in windy areas where dwarf
cultivars are more suitable. Post-harvesting issues may arise for unfamiliar cultivars
(or hybrids). Cultivars with different growth cycles will also lengthen the harvesting
period, leading to an increased logistic complexity and potentially lower profit margins
at market.
Lescot and Staver (2010) provide a practical guide of quality standards for buyers
who are placing an order or receiving a batch of suckers for direct planting or plants
produced in a nursery (Table 1).
Table 1: Summary tables of standards
Suckers/corms for direct planting
Size of suckers and corms
At least 12 cm in diameter
Suckers/corms health
Removal of roots/peeling to reduce contamination with
pests/diseases;
Tolerance: 31
Creamy-white corms resulting from elimination of insects
galleries, nematodes, bacterial/fungal diseases;
Tolerance: 2
Pseudostems
Cross section without off-coloured rings or liquid or brownish
spots;
Tolerance: 0
Plants produced in the nursery
Plant size
Last leaf 20-cm length, oldest leaves larger than young ones
Tolerance: 1
Height of plant
Not to exceed two times height of pot
Tolerance: 5
Off types
Dwarfism, gigantism, mosaic-like, variegated,
chlorotic/necrotic leaf patches, droopy leaves
Tolerance: 1
Container
Damage/loss of substrate
Tolerance: 2
Source: Lescot and Staver (2010)
1
Lescot and Staver (2010) included a ranking using a % tolerance to identify the relative importance of non-compliance
with each standard. The percentages are, however, not confirmed by experimental data. They have been recoded here,
whereby 0 = zero-tolerance and 5= highest tolerance.
10
IV.
Sanitary factors related to Musa planting materials
In sexually propagated crops, many pathogens are filtered out in the process of seed
production. By contrast, without control measures traditional farmer planting materials
for vegetatively propagated crops actively promote the dispersal of pathogens. The
most important seed borne pests and diseases for Musa planting material are
nematodes, weevils, Fusarium wilt (race 4), and viruses including Banana Bunchy
Top Virus (BBTV), Banana Streak Virus (BSV) and bacterial wilts. Reducing the
incidence of these pathogens can lead to greater productivity, even without additional
inputs.
Ensuring the sanitary quality of traditional planting material is fairly straightforward
with regards to weevils and nematode infestations, yet many farmers are unaware of
methods that can be used to obtain clean suckers (e.g. thermal treatment 1 and/or
paring). For fungal, bacterial and viral infections, the only option is to eliminate the
material from the farm. This requires sound diagnostic capacity, which is frequently
challenged by a lack of information available to farmers. As a result, germplasm
exchange continues to play a significant role in the dissemination and introduction of
many Musa pests and diseases. Both informal networks, moving planting materials
among farms and villages and across borders, and formal networks (e.g. research
stations and botanical gardens) may play a part in this process, especially where
effective quarantine measures are unavailable or poorly implemented (Macharia et
al., 2010; Blomme et al., 2012).
Although tissue cultured plantlets are generally disease and pest free, they can
harbor viruses and bacteria, if indexing is not carried out on the donor plants. The
sanitary quality of plantlets produced by tissue culture enterprises is frequently
challenged by the lack of standards for quality management during the production
process, plant health certification, and regulatory procedures. Regional
harmonization of certification schemes would greatly facilitate germplasm movement
between countries (Dubois et al. , 2013 – in press).
A brief description of the major pests and diseases affecting Musa planting materials
is given below.
a. Main seed-borne diseases of Musa planting materials
i. Fungal diseases
Fusarium oxysporum
Input provided by M. Dita
Fusarium wilt (Foc) is a serious problem on many banana cultivars. Different races of
F. oxysporum sp. cubense have been identified based on their pathogenic potential
to affect different subgroups of Musa spp. The disease was first recognized almost
150 years ago in Australia and became notorious in the 1950s for the destruction of
the ‘Gros Michel’-based export banana plantations in Latin America. It was the
progressive decline of plantations of this cultivar due to Fusarium wilt that led to the
adoption of cultivars in the AAA ‘Cavendish’ subgroup as the main export banana
types. Gros Michel (AAA) and related cultivars (Coco, Highgate, others), Apple
(AAB), Prata (AAB), Prata Anã (AAB) and Pisang awak (ABB) are susceptible to race
1; Bluggoe subgroup (ABB), are susceptible to race 2. Cavendish (AAA) subgroup
and plantains AAB are resistant to race 1 and 2, but susceptible to tropical race 4
(TR4). TR4 also affects many other cultivars (Ploetz, 2007).
1
Thermal treatment or thermotherapy refers to hot- and boiling-water treatment of suckers. This treatment consists of
dipping suckers, usually pared (although cleaning efficacy is not improved, this allows visual detection of weevil galleries),
in hot (52°C for 20min) or boiling (100°C for 30s) water. This is sufficient to kill all nematodes and weevil eggs adhering to
the sucker and helps to reduce pest and disease related yield loss (Colbran, 1967; Tenkouano et al., 2006; Hauser,
2007).
11
Plant infection occurs mainly by the secondary and tertiary roots. Once the pathogen
is established, it will colonize vascular vessels, release toxins and move upward in
the xylem. Pathogens then colonize roots, rhizome, pseudostem and leaf petioles.
Fruits are not affected. The pathogen moves from the infected rhizome of the maiden
plant to the follower suckers through the vessels of the growing buds. Symptoms
usually do not develop on emerging suckers until very advanced stages of plant
growth, usually at flowering stages. Symptomless, but infected suckers are therefore
an efficient and probably the most important way that pathogens are spread in
smallholder farming systems. In addition, run-off and irrigation water, flooding and
soil movement can disseminate fungal structures (conidia and chlamydiospores) from
plant to plant and over long distances.
Dry periods, soils with a high water table and co-infection with nematodes are factors
that exacerbate disease development. Dominguez et al., (1995), reported that
increases of NH4 in soil speeds up development of the disease. There is also a
consensus among growers and workers that high urea application increases
Fusarium wilt. Greenhouse experiments have confirmed that both nematode infection
and urea application increase disease expression (Chaves, unpublished)
A susceptible banana plant infected with Foc rarely recovers. However, poor growth
of the clump may continue for some time and many infected suckers may be
produced before the clump finally dies (Moore et al., 1995). In addition, through
perpetuation of the disease in the soil, land value for Musa cultivation is also affected.
Infected plants normally don't produce bunches and those that are able, produce
poor and low value bunches. Currently, the most efficient means of control is the use
of resistant cultivars and quarantine programs to avoid the distribution of infested soil
and planting materials (Moore et al., 1995). In 1983, Fusarium wilt (Fusarium
oxysporum f. sp. cubense or Foc) motivated the development of tissue culture
technology for mass propagation of disease free plantlets for commercial planting in
Taiwan. The use of tissue-cultured plantlets successfully reduced the spread and
severity of the disease. The lack of Foc-free planting materials and inefficient infected
plant eradication are major contributors to the steady spread of this disease.
High quality planting material should be free of Foc. Resistant cultivars or cultivars
inoculated with beneficial endophytes also constitute improved quality, as opposed to
planting materials where Foc spores have accumulated. Infestation leads to reduced
productivity and value of planting materials. Infected planting materials are
symptomless and require advanced molecular diagnosis, which is only available for
tropical race 4 (Dita et al., 2010). Farmers can identify problems through close
observation of the mother plant and avoiding the use of suckers from infested mats.
Tissue culture is able to provide Foc-free planting materials. It is unclear, however,
whether the procedure of tissue culture itself is able to clean infected material.
Recently, with the threat of Foc TR4, indexing has been requested even for tissueculture plantlets
ii. Viral diseases
Banana Bunchy Top Virus
Input provided by P. Lepoint
Banana bunchy top disease is the most serious of the viral diseases affecting
bananas and plantains. Banana bunchy top nanovirus is one of the most destructive
pathogens affecting Musa spp. The disease negatively impacts production, trade and
international relationships.
BBTV has been found in all banana producing regions of the world except Latin
America. Australia and Fiji have suffered from devastating epidemics at beginning of
the last century. In recent years disease has decimated Cavendish production in
Pakistan. Since 1991, BBTV has become a major concern in many Asian and Pacific
countries. Transmission is through infected suckers and via infection by the aphid
Pentalonia nigronervosa.
12
Pentalonia nigronervosa has a worldwide distribution with a host range that includes
M. textilis and other species in the Musaceae. Species in several plant families
including Araceae (Alocasia sp., Caladium spp., Dieffenbachia spp., Xanthosoma
sp.), Cannaceae (Canna spp.), Heliconiaceae (Heliconia spp.), Strelitzeaceae
(Strelitzia spp.) and Zingiberaceae (Alpinia spp., Costus sp., Hedychium spp.) are
also hosts (Wardlaw, 1961).
BBTV is a systemic virus. Following infection, the BBTV particles invade the phloem
and migrate to the meristem of the infected plant, eventually radiating to all new plant
parts (leaves, bunch, etc.) and suckers. After aphid-mediated inoculation, symptoms
generally do not appear until two or more leaves have developed (Magee, 1927).
This period can vary between 19 days in summer to 125 days in winter (Allen, 1978).
Suckers produced on an infected mat generally develop symptoms before reaching
maturity (Magee, 1927). Affected plants produce progressively shorter leaves, giving
the plant it’s characteristic “bunchy” appearance. Control includes the destruction of
infected plants, application of insecticide to kill the aphids and use of virus-free
planting material. Infected plants may produce a deformed bunch, but frequently they
do not produce a bunch at all (Thomas et al., 1994; Molina and Valmayor, 2000).
Disease management should also include strict quarantine legislation, consisting of
systematic control on the source and movement of planting material.
In studies of outbreaks of bunchy top in commercial banana plantations, Allen (1978,
1987) showed that the average distance of secondary spread of the disease by
aphids was only 15.5-17.2 m. Nearly two-thirds of new infections were within 20 m of
the nearest source of infection and 99% were within 86 m. If a new plantation was
located adjacent to a diseased plantation, the chance of spread of bunchy top into
the new plantation within the first 12 months was 88%.
Most cultivars are susceptible to the disease and resistant landraces varieties are not
well documented. Yield loss up to 50-80% has been observed. For plants infected in
the pre-flowering stage, 100% yield loss can be expected. Followers of infected
mother plants most the times do not produce bunches. For plants affected later in the
growth cycle, general reduced productivity can be expected, due mainly to a reduced
bunch size. The disease is only transmitted via the aphid vector and subsequently
through infected planting material. No survival in soil, or mechanical transmission has
been observed. The disease does not alter the sensory quality of the bunch, however
a small bunch is less marketable. Advanced diagnosis methods use TAS-ELISA or
PCR. Detection can be done using any plant part, however, optimal diagnostics is
carried out on samples of a section of the youngest leaf, including the midrib.
Farmers may diagnose BBTV through observation of symptoms. However, although
symptomatology is the easiest of the detection methods, it is not always reliable for
viruses affecting Musa spp. Mixed infections are frequent and symptoms are not
always clear. Symptoms caused by different viruses can be similar and infected
plants may even be symptomless (Thomas, 2000).
Few technologies exist to clean planting material once infected with BBTV. Use of
certified virus-free planting material, preferably from BBTV-free areas, is condoned.
Alternatively, in BBTV infested areas specific control measures should be employed,
such as the use of insecticides or insect-proof netting in tissue culture production or
macropropagation. Good cultural practices consist of reducing aphid populations
through deleafing, proper plantation management e.g. establishment of new plots
outside existing diseased plots, regular evaluations of plantation health status and
uprooting of infested stands as soon as possible.
Subsistence banana farmers in developing countries are most affected by BBTV,
since they lack access to disease free planting materials and lack the capacity to
implement a sustained eradication and rehabilitation programme. In countries like
Australia and Taiwan, BBTV is effectively managed through virus-indexed planting
materials and the political will to implement a rational quarantine, eradication, and
rehabilitation program. Similarly, corporate large-scale plantations have less
problems with BBTV, as they implement strict disease monitoring and eradication
practices (Molina and Valmayor, 2000).
13
Other viruses
The Banana Bract Mosaic Virus (BBrMV): is transmitted by vegetative propagation
and tissue culture, as well as by aphids: mainly Rhopalosiphum maidis, Aphis
gossypii and Pentalonia nigronervosa. Up to 40% yield loss has been recorded in the
Philippines, where comprehensive rogueing and sanitation programmes are
implemented (Magnaye, 1994). Fruits fail to fill on infected plants in India (Jones,
unpublished). On export bananas, streaks on the fruit are a cause for rejection. The
virus can be detected by ELISA in extracts of leaf laminae, midribs and flower bracts,
using BBrMV-specific monoclonal and/or polyclonal antibodies. Geographical
distribution: Philippines, India, Sri Lanka. Farmers may identify the disease using the
following progressive development of symptoms: dark coloured, broad streaks on the
bracts of the inflorescence. A shortening of bunch internodes is also characteristic.
After removal of dead leaf sheaths, the presence of large dark coloured stripes of
varying length, sometimes with a mosaic pattern, is diagnostic of the disease.
Greenish to brownish broad, irregularly scattered spindle streaks develop along the
petioles, possibly with raised veins (Diekmann and Putter, 1996).
Cucumber Mosaic cucumovirus (CMV) is present in most banana producing
countries. The virus has more than 300 known hosts including cucurbits and
solanaceous plants commonly cropped in association and/or in neighbouring areas to
banana fields. In the Windward Islands in the Caribbean, disease incidence is high
and associated with transmission by aphids, due to the presence of virus in reservoir
weeds, such as Commelina spp. and association with tomatoes and cucumber
plants. CMV is transmitted as BBrMV. Additional vectors include Rhopalosiphum
prunifoliae and Myzus persicae. Occasionally, severe outbreaks of CMV occur.
Plantlets derived from tissue culture are more prone to infection. Numerous strains
exist, with variable virulence for banana and plantain. The heart-rot strain found in
Morocco is particularly destructive. The virus can be reliably detected by ELISA using
polyclonal and monoclonal antibodies for CMV, or by mechanical inoculation to a
range of diagnostic test plants, e.g. Chenopodium amaranticolor, C. quinoa and
Vigna unguiculata (Francki et al., 1979). Farmers may identify the disease using the
following symptoms: mild or severe chlorosis, chlorotic streaking or flecking, mosaic
patterns and leaf distortion. The heart-rot strain causes severe yellowing and
necrosis, which begins on the cigar leaf and spreads into the pseudostem. Eventually
the pseudostem rots. Uneven ripening has been associated with the virus.
Suckers produced from infected plants may show no symptoms. In some varieties,
high temperature may suppress symptoms. Symptoms have often been confused
with those of BSV (Diekmann and Putter, 1996). CMV is frequently found cohabiting
with BSV in the same plant.
For CMV, virus-free plantlets have been obtained by tissue culture from heat-treated
suckers or from lateral buds developed on heat-treated rhizomes (Diekmann and
Putter, 1996). CMV management for seed production in field should include weed
control and avoiding association or neighbour solanaceous and cucurbitaceous
plants.
BSV
Banana streak badnavirus (BSV) is transmitted by vegetative propagation to 100% of
progeny plants. Field spread is by mealy bugs and at least six species are today
confirmed of transmitting BSV. Among them are citrus mealy bug, Planococcus citri,
Planococcus minor, among others. There is evidence that BSV is seed-transmitted in
Musa (Daniells et al.,1995). Integrated sequences of DNA of virus are present in the
M. balbisiana genome and under stress are activated and become episomal causing
new infections. The presence of BSV endogenous pararetrovirus (EPRV) in the
genome of interspecific triploid (AAB) and tetraploid (AAAB) varieties results in
severe limitations on the use of micropropagation. BSV infection may arise from
activation of viral sequences that are integrated into the Musa genome and activated
14
through tissue culture of Musa spp. (Harper et al., 1999; Delanoy et al, 2003).
Indeed, the tissue culture process itself is suspected of activating the BSV EPRVs in
virus-free shoot tips, especially in plantain species. Tissue cultured plantlets require a
quarantine period to be sure that they are BSV-free (Jones and Lockhart, 1993). In
vitro techniques are not recommended for the multiplication of the AAB varieties,
especially plantains and AAAB varieties. These varieties can be multiplied from local
mother plants for distribution to farmers within the same region. However,
micropropagated plantlets of these cultivars should not be exchanged between
countries. Other varieties, especially those with the Musa acuminata genome,
present no risk of BSV EPRV activation during tissue culture (Lescot and Staver,
2010). Yield losses between 7-90 % have been observed (Jones and Lockhart,
1993). Disease incidence varies between countries and this may be related to strain
differences and/or vector activity (Diekmann and Putter, 1996).
Farmers may recognize the following symptoms, depending on the isolate and
cultivar: necrosis of the pseudostem, smaller bunches, reduced plant growth and
yield, and distortion of fruit morphology and spotting of peel and pulp. The most
typical disease symptom is, however, chlorotic streaking of the leaves, which can turn
necrotic with aging. Some isolates of BSV produce severe necrosis, which begins
with the cigar leaf and results in internal pseudostem necrosis and plant death.
Symptomless infection occurs frequently. Symptoms appear sporadically, and may
be absent on leaves produced during many months before reappearing. Symptom
appearance and severity are associated with temperature changes, but the precise
correlation has not been experimentally determined. Symptoms are often confused
with those of CMV. Serological detection of BSV is complicated by the occurrence of
a wide degree of serological diversity among virus isolates, some of which are
unrelated serologically to each other (Lockhart and Olszewski, 1993). A recently
developed antiserum raised against many isolates is capable of detecting all known
isolates by ISEM in partially purified extracts, even in asymptomatic leaf tissue
(Lockhart, unpublished in Diekmann and Putter, 1996). The best reliable diagnostic
procedure is IC-PCR. Several strains of the virus have been identified (BSV-O’lawai;
BSV-Goldfinger; BSV-Mysore; BSV-Imove; etc.); and specific primers have been
developed for detection.
Thermotherapy followed by apical meristem culture failed to eliminate or reduce the
titre of the related SCBV in sugarcane (Lockhart, unpublished in Diekmann and
Putter, 1996).
iii. Bacterial wilts
Input provided by E. Alvarez and G. Blomme
Bacterial wilts are caused by Ralstonia solanacearum Smith, phylotype II (Moko
disease) and Xanthomonas campestris pv. musacearum (Xanthosomas wilt or BXW).
Reported for the first time in the 1930’s in Sulawesi, the disease epidemic led to
quarantine regulations that prohibited the translocation of planting materials to other
islands of Indonesia. More recently, the disease has wreaked havoc in West Java
and the southern island of Sumatra and the Philippines. Infected plants are subject to
fruit rotting, rendering the fruits unfit for human consumption (Molina and Valmayor,
2000). In 2001-02, the disease was discovered in Uganda, DR Congo and Rwanda,
where it was associated with up to 50% yield loss in affected farms. No cultivars in
East Africa were resistant, although East African banana cultivars were less affected
than ABB and AAB cultivars. A large scale information campaign to banana farmers,
included plantation sanitation measures and the avoidance of introduction through
the use of clean planting materials (Karamura et al., 2010).
Insects that feed on male buds transmit the bacteria. Subsistence banana farms are
most affected as farmers do not sanitize and remove male buds. Large commercial
plantations, by contrast, usually manage the disease by removing male buds as soon
as the false hands appear. At the same time, fruits are protected with plastic bags
and strict monitoring and eradication of infected plants is carried out (Molina and
Valmayor, 2000).
15
High quality planting material is free of bacterial cells, preferably certified planting
materials, produced in sites free of Moko disease. Ralstonia solanacearum can
invade seed cells; and, depending on the number of bacterial cells, the pathogen
may cause seed death in the nursery, or the plant remains asymptomatic until it is
transplanted to the field. Lesions caused to suckers, either mechanically or by
insects, may favour infection by R. solanacearum. Yield losses up to 100% may be
observed, as infected plants deteriorate progressively and die, or the bunches
produced are of low quality and unmarketable. Disease foci must therefore be
isolated, reducing the productive area and motivating many farmers to change crops.
The bacteria disseminate easily through run-off, colonizing and compromising new
Musa crops. Diagnosis can be done through real-time PCR for the highly sensitive
and specific detection of R. solanacearum in asymptomatic plants, soil, and water.
Multiplex PCR is used to classify phylotypes and sequevars. Vigilant farmers may
observe the following progressive symptomatology of Moko disease, which begins in
leaf folds, dehydrating the tissue. Also, on cutting the pseudostem and corm, necrotic
vascular bundles can be seen. Cleaning methods include the mass propagation of
planting materials from carefull selected mother plants that are free of R.
solanacearum. Mass propagation should include thermotherapy (thermal chambers),
sterilized substrates, and automated control. The surface of corms should always be
disinfected before planting in the field and care should be taken to disinfect tools
before every new plant, using a disinfectant solution of 5% NaClO (household
bleach) or a 20% iodine solution (Paull and Duarte, 2011).
Cultivars showing genetic resistance to R. solanacearum will also provide superior
planting materials.
Good management with respect to R. solanacearum include use of clean planting
materials, regular renovation of Musa plantations, biological diversification of soils
and adequate planning of weed management to reduce R. solanacearum inocula,
recovery of rich and diverse soils for later planting with clean quality seed, linking the
seed production system with a biotechnology and/or genetic improvement program to
“plant quality healthy materials in healthy soil” and routine follow-ups by certified
laboratories to determine plant health, focusing on nurseries producing certified
planting materials.
b. Main pests that influence seed production or availability
i. Plant parasitic nematodes1
Input provided by D. Coyne, S. Hauser and K. Jacobsen
The aboveground symptoms of plant parasitic nematode damage to bananas and
plantains are related to an impaired uptake of nutrients by the plant, following root
damage caused by nematodes. This results in reduced plant growth, lengthening of
the growth cycle and reduced bunch weight. The weakened root system can also
lead to toppling of the plant before harvest, particularly during strong winds (Sarah et
al., 1996). Invasion of the central cylinder of the corm, and by homology that of the
roots, is generally not observed, although they can penetrate young vascular tissue.
The cortical damage they inflict may facilitate invasion by secondary fungal
pathogens causing additional damage to vascular tissues (Speijer and Sikora, 1993;
Pinochet, 1996; Sarah et al., 1996). Yield loss associated with nematode infection
depends on the (race of) nematode species present. Endoparasitic lesion forming
nematodes are generally more damaging than root knot nematodes, semiendoparasites and ectoparasites. Cultivar susceptibility and abiotic conditions will
further impact the effect on productivity and value of the crop.
Where export banana plantations will commonly use crop rotation in combination with
clean planting materials and nematicides, nematode management in small-scale
1
This section concerns only plant parasitic nematodes. From here on the term “nematode” will refer by default to plant
parasitic nematodes
16
tropical farming systems aims to integrate four main strategies (Bridge, 1996): (1)
preventing the introduction and spread of nematodes, (2) direct non-chemical,
cultural and physical control, (3) encouragement of naturally occurring control agents
and (4) maintenance and enhancement of the biodiversity inherent to multiple
cropping and multiple cultivar traditional farming systems to increase the available
resistance or tolerance to nematodes.
Tissue culture derived plantlets are more susceptible to nematode infection. Planting
materials should preferably have cortex and roots free of plant parasitic nematodes,
additional colonization with beneficial endophytes can further improve the quality by
increasing resistance to soil-borne pathogens. Cultivar resistance and tolerance is
often species-specific and can further improve productivity of the Musa plantation.
Diagnostic methods consist of extraction of nematodes from a subsample of the roots
collected in the field and/or from the outer layer of the cortex, followed by species
identification and determination of infestation levels, using a light microscope.
Molecular diagnostic tools are being developed, but currently still not available.
Farmers could learn to identify root necrosis in the field –but very few have been
trained. Symptoms include blackened root tissue and corm surfaces.
Several effective techniques exist to clean planting materials: paring in combination
with hot-water treatment (20 minutes at 52°C); boiling water treatment (30 min at
100°C), which can also be carried out without paring (trimming of the roots suffices);
pralinage using a nematicide mixed with mud, and rubbed over the corm; pralinage
using neem or other nematicidal plant residues (controversial results); clean planting
material can also be obtained through macro- or micropropagation. Good
management practices (e.g. mulching, fertilizer application, irrigation during dry
season, propping) further increase tolerance for nematodes.
ii. Weevils
Of the insects affecting bananas, plantains and ensete, the larvae of the banana
borer weevil (Cosmopolites sordidus) cause the most damage. Most egg-laying is in
the leaf sheaths and rhizome surface. Severe yield loss can occur due to the
tunnelling action of the larvae as they develop inside the corm of Musa plants,
leading to reduced growth, bunch weight and increased toppling. Originally from
southeast Asia, banana weevils are now a problem in most banana producing
regions, although mostly on east African cooking bananas, plantains and ensete
(Gold and Messiaen, 2000).
Weevil trapping is a useful tool to estimate risk of damage before planting. If weevil
trapping reveals presence of C. sordidus, insecticide may be used at planting and
applied at the base of the plant periodically to limit population establishment and
build-up. Control against the adult weevil is best done in the wet season as they are
most active then. Suckers can be effectively cleaned through paring and heat
treatment. Care should be taken to store pared and cleaned suckers away from
possible new infection before planting (i.e. cover the pile of suckers with a tarp).
Cleaned suckers can additionally be dipped in a 20% neem solution (Azaridichta
indica) at planting to further protect young plants during the first months after
planting. Reduced oviposition rates, hatching of eggs and corm damage were
observed by dipping suckers into a Neem (Azaridichta indica) seed powder solution
(20%) (Messiaen, 2002), but have yet to be commercialized. Resistant genotypes
also exist, such as ‘Yangambi km5’, ‘Pisang Mas’, ‘Calcutta 4’ and M. balbisiana
types, which can be incorporated into breeding programs (Gold and Messiaen, 2000;
Messiaen, 2002).
DEGENERATION
Some thoughts:
What does the concept of "degeneration" mean, particularly for Musa?
17
To my knowledge, the term comes from potato-pathologists although some
other crop-pathologists have adopted the term. I am not sure that it is
transferrable to Musa spp.
I have the following two definitions of degeneration:
1. “A steady decline in yield without overt disease symptoms”. You can have
potatoes that are infected with virus and when viewed in isolation (not next to
healthy potatoes), look healthy although over a 10-year period, there has been
a steady decline in yield. NB. Viruses may not be the only cause of yield
decline and may be due to a range of soil health issues. (A. Geering via email)
2. “Seed degeneration is the build up of diseases in potatoes over seasons, as
a result of replanting tubers infected with viruses, bacterial wilt or other seed
borne diseases” (Gildemacher et al, 2007)
The following questions spring to mind:
Does the concept of degeneration provide a useful framework to consider
sanitary quality of Musa planting materials?
How closely is the concept linked to the “observation of disease (symptoms)”
For example, if a farmer sees no overt symptoms = degeneration?
Or only when a scientist sees no overt symptoms?
And what about the search magnitude (eye /microscope /molecular)?
Is it necessary to adopt this term?
How does latent infection relate to degeneration?
What mechanisms are involved (at a cellular level)?
It might be more interesting and relevant, in the larger framework of planting
materials, to consider the implications of co-infections with multiple
pathogens. A plant is seldom infected by only one pathogen (pest or disease)
and there is little information available on multi-pathogen infections (also due
to difficulties setting-up multi-species field trials). For example, there are
documented reports of opportunistic secondary fungal infections following
nematode root penetration Concomitant and higher damage has also been
documented when weevils and nematodes occur together. Some nematodes
are associated with viral infections (although not species common to musa).
Damage caused through pathogen-synergy is something that has received
only limited attention in the literature)
V.
Available technologies for multiplication – rates, time, costs, infrastructure
requirements
Five methods are used to obtain Musa planting materials. Each method has specific
requirements in terms of facilities and equipment, generates planting material at a
characteristic rate and has particular risks of pest and disease contamination.
In recent years, two excellent, practical, illustrated guidelines have been published.
Lescot and Staver (2010) and the more extensive Staver and Lescot (2013).
Additional references are mentioned, where relevant, below.
a. Suckers extracted from a field in production
Facilities and Equipment: An existing Musa plantation, a coffee digger or heavy stake
and a machete or large cutlass
Rate of production: The rate of multiplication of suckers is at the pace of 15 to 20 per
year depending on cultivar and influenced by environmental factors and management
practices (Ortiz and Vuylsteke, 1998). For example, dessert bananas (AAA) have a
poly-archic architecture that produces relatively large numbers of well-developed
suckers at maturity of the plant crop. In contrast, the emergence of plantain suckers
18
follows a hierarchic pattern, with inhibited suckering caused by the hormonemediated apical dominance of the mother plant (Swennen, 1984; Ortiz and
Vuylsteke, 1994). Cultivars with high apical dominance show inhibited sucker
development, while clones with low apical dominance will produce one or two welldeveloped suckers (regulated suckering behavior) or many developing suckers (nonregulated suckering behavior; Ortiz and Vuylsteke, 1994). Factors that stimulate root
branching, such as soil fertility and mulching, generally have a beneficial effect on the
number of suckers produced (Swennen, 1984; Blomme, 2000; Jacobsen, 2010).
Other: Over-extraction or careless extraction of suckers may result in weakened plant
support and stem toppling. Suckers should be pared and heat-treated. If boiling water
treatment is used, paring is not obligatory (although preferred, to identify weevil
damage). Care should be taken to disinfect tools before every new plant, to avoid
transmission of bacterial diseases such as Moko (Paull and Duarte, 2011): a
disinfectant solution of 5% NaClO (household bleach) or a 20% iodine solution can
be used to wipe or dip tools.
References: Tenkouano et al. (2006); Hauser (2007); Paull and Duarte (2011);
Relying on the natural regeneration of plants for the supply of planting materials is a
slow process, however, and may not yield sufficient planting material to expand,
renew or establish new plantations. Several multiplication techniques have been
developed to increase the number of suckers.
b. Suckers produced in field multiplication plots
Facilities and Equipment: Suckers or corm pieces can be used to plant a high density
stand or mats can be selected in an existing plantation. When plants initiate flower
formation, but well before flower emergence, plants are decapitated to stop further
flower or bunch development and stimulate sprouting of abundant suckers. False
decapitation or bending of the pseudostem can also be used, which impedes
flowering, but maintains the mother plant, while also stimulating the sprouting of
suckers. Essentially through destruction of the apical meristem, axillary bud growth is
stimulated.
Propagation: by meristem manipulation
Rate of production: 10–20 suckers per mother plant
Other: Suckers should be pared and heat-treated before planting (cfr sanitary quality,
above).
References: De Langhe (1961), Wilson et al. (1987b)
c. Detached corm techniques
i. Suckers from microcorms, grown out in nurseries
Facilities and Equipment: A well-developed banana or plantain corm contains several
axillary buds, which essentially host meristems of different ages and stages of
development (Kwa, 2003). These small, cone-shaped suckers (200–300 g), called
peepers, are extracted from a production field or a sucker nursery, treated and then
planted into a nursery for 6–8 weeks, until plants reach an appropriate size for
transplanting. Plants can be grouped by height and number of leaves to ensure more
uniform growth and time to harvest.
Propagation: by bud manipulation
Rate of production: buds are harvested from an existing Musa plantation, between 25 per stand, and replanted in the nursery (one shoot per microcorm or bud).
Other: Suckers are pared, treated with surface disinfectant and then planted into
small nursery bags filled with clean substrate
References: Lopez (1994), Rosales et al. (2010)
19
The following two techniques (macro- and micropropagation) are useful to provide
large numbers of replacement plants where diseases have reduced plantations or to
locally multiply newly introduced varieties for distribution.
ii. Macropropagation: activation of latent buds through physical
destruction of the apical dominance
Plants issues de bourgeons secondaires (PIBS), Plants issues de fragments de tige
(PIF), or CFS (corm fragment shoots)
Facilities and Equipment: Sword corms (minimum 12–25 cm diameter or 150–400 g)
or pieces of larger corms, peeled and stripped completely of leaf sheathes, are
placed in wet sawdust in a humidity chamber made of plastic sheeting. The
destruction of the main growing point of the sucker releases the axillary buds at the
base of each leaf sheath for sprouting. The resulting shoots are carefully excised and
transferred to nursery bags, under similar conditions to microcorms, until the plants
are ready for transplanting. Set-up of macropropagation chambers should preferably
be in warmer climates (in the tropics at altitudes below 1000m asl), to reduce the
latency period.
Propagation: by meristem manipulation
Rate of production: 8–60 plantlets/corm/4 months
Other: Suckers should be pared, treated with a fungicide and dried in the shade for
one day before planting. Plantlets are extremely vulnerable for drought and should be
irrigated when planted in the dry season.
References: Munoz and Vargaz (1996); Auboiron (1997); Kwa (1997, 2002, 2003);
Nkakwa and Yemin (2003); Tenkouano et al. (2006); Njukwe et al. (2007); Mekoa
and Hauser (2010);
iii. Micropropagation: Tissue culture derived plantlets
Facilities and Equipment: Suckers should preferably be extracted from a region free
of diseases, subject to quarantine, tested for disease presence and then cleaned, if
necessary. The resulting shoot tips are disinfected before being introduced into the
sterile lab. Under controlled laboratory conditions, small corms are then pared down
and disinfected prior to the extraction of the shoot tips. The shoot tips are individually
excised and transferred to a growth and rooting medium. Each shoot tip gives rise to
3-20 new shoot tips. These are again cultured to multiply at the same rate. No more
than 10 subcultures should be done from an initial shoot tip (about 1000 – 2000
tissue culture plantlets) to minimize the risk of off-type plants. The tiny plants are then
sized and transplanted into trays or small individual pots and set out in a hardening
nursery with high humidity and limited light, during a period of about 4-7 weeks.
During this period the small, tender plants gain size and leaf area. Plants are
transplanted into larger bags filled with sterile medium and moved into a weaning
nursery. Little by little they adapt to higher sunlight and lower humidity found under
field conditions. In 4-7 weeks plants are ready for transplanting.
Within the tissue culture production chain, there are principally three key players: (a)
tissue culture producers, who initiate, multiply and root plantlets in specialized
laboratories; (b) tissue culture nurseries, which wean plantlets in humidity chambers
and subsequently harden them in screen houses; and (c) farmers using tissue
culture.
Rate of production: 1000 tissue culture plantlets per shoot tip
Other: The organization of clean source material is a critical part of the tissue culture
procedure. Suckers should be pared, treated with a fungicide and dried in the shade
for one day before planting; afterwards they should be maintained in an area free of
banana plants or in an insect-proof enclosure. Once planting material has been
verified as virus free, it can be planted in large pots in a screen exclusion house to
ensure that there is no contact with virus-bearing vectors. Such material can serve as
a regular source of small corms for new shoot tips.
20
Reference: Vuylsteke (1989); Israeli et al. (1995); Singh et al. (2011)
Plantlets obtained through macropropagation have the uniformity of micropropagated
plantlets, while being less prone to post-establishment stress and loss in the field.
However, macropropagated plantlets have lower survival rates during the hardening
stage in the nursery compared to micropropagated plantlets. Macropropagation is
relatively simple and requires minimum investment. Corms from pre-flowering or
harvested plants are suitable for macropropagation methods, but even suckers from
field multiplication plots could be used (Tenkouano et al., 2006). Micropropagation,
by contrast, can yield in even larger quantities in shorter periods of time, allowing for
faster and better distribution of existing and new cultivars, including genetically
modified banana (Tenkouano et al., 2006). Micropropagation is, however, more
expensive and depends on the availability of tissue culture laboratories.
Macro- and micropropagated plantlets allow the timely production of fruit (also known
as Crop Timing Plantation or CTP) in periods of high demand (Ronen et al., 2002).
However, although both propagation methods provide essentially pest and disease
free material, the need for pest and disease control is only delayed and the presence
of banana viruses may remain problematic.
VI.
Farmer knowledge and practices for management of Musa planting materials
a. Description of the main traditional practices of seed management by farmers,
including maintenance of genetic diversity
Worldwide, seed is predominantly produced, selected and stored by farmers,
particularly in developing countries. For Musa, the majority of farmers provide their
own planting material, with additional material occasionally sourced via the informal
system (Shamebo, 2000; Banful, 2000; Hauser and Amougou, 2010; Staver et al.,
2010).
Local seed has some advantages. It is low cost and convenient with a focus on
preferred and locally adapted cultivars. Large quantities of Musa planting material are
difficult to transport over long distances, being bulky and perishable. Local seed is
available even in regions distant from markets. Informal seed systems are also
generally adaptively flexible, with a mix of varieties that adjust well to a range of local
conditions (Thiele, 1999; Almekinders et al., 1994).
Human strategies to retain, maintain and distribute seed for planting, has created a
wealth of cultivar diversity. Farmers’ management of this diversity, both within and
among cultivars, can be seen as a strategy to cope with risk and a means to create
greater resilience, enabling food security (Kahmen et al., 2005; Richards et al.,
2009).
Notwithstanding the apparently robust and sustainable nature of informal seed
systems, there are inherent disadvantages in relying solely on one’s own production
and local trade. The yield stability achieved through varietal mixtures often goes hand
in hand with a lower yield potential compared to improved varieties or planting
material available through the formal seed system (Almekinders et al., 1994). The
lack of standardization of informal seed systems can impact on all levels of genetic,
sanitary or physiological quality of planting materials, increasing seed-related yield
loss. Farmers frequently use their own planting materials or that obtained from
neighbors, unaware of seed-borne pests and diseases and oblivious to their spread
(Schill et al., 2000; Blomme et al. , 2012). Furthermore, once a sucker is detached
from the mother plant, it is impossible to ascertain the cultivar (genetic quality). A
survey carried out in Southern Cameroon (Hauser and Amougou, 2010), showed that
farmers were indeed frequently unaware which Musa cultivar they had planted. In line
with such findings, another survey in Cameroon and Nigeria, showed that all farmers
and plantlet producers were in favor of a certification system to guarantee sanitary
and genetic quality of Musa planting material – indicating that this is a serious
constraint where suckers or plantlets are purchased (Wendelboe and Göransson,
2006).
21
Bunch characteristics have been cited as important sucker selection criteria for
farmers in East Africa (Gold et al., 2002a) and the Cameroon Highlands (Jacobsen,
2010), indicating that selection is often carried out before detaching from the mother
plant or that the genetic quality is ensured by the provider or trader of the planting
material. In Uganda, one of the selection criteria farmers used when determining
which cultivars to grow was “availability of adequate planting material” – a little over
50% of the farms used this criterion. Quick maturing cultivars that produce many
suckers and are appreciated for their taste may thus become widespread faster.
Whereas cultivars with slower maturation and/or sucker production, whose
characteristics hold certain ritual, cultural or esthetic value rely on dedicated farmer
maintenance (Gold et al., 2000b). Among the Indians of Central America, selection is
reportedly based on sanitary and physiological quality criteria and integrated into the
planting process, whereby most farmers will plant as many varieties as possible to
insure against biotic and abiotic threats (Johannessen, 1970)
In intensive production systems, banana yields tend to fall from three to five years
after planting, and decline rapidly after ten to fifteen years 1. For existing yields to be
maintained, a cyclical process of replacement of old for new plants must be
undertaken.
Conventionally, banana companies produced their own planting materials through
practices akin to those of small- and medium-scale farmers. Propagation practices of
commercial banana plantations before the advent of micropropagation, anno
1956, are described in Les principales cultures Congo Belge : « Les variétés
comestibles ne sont jamais propagée par graines (sauf dans les travaux de
sélections), car elle n’en produisent que très exceptionnellement. On les reproduit
soit par des grands rejets de 4 à 6 mois, soit par des petits rejet s de 2 à 3 mois, soit
par des fragments de rhizome. L’emploi de grands rejets de 4 à 5 pieds de hauteur et
munis d’une souche bien développée est une méthode excellente, très employée au
Congo. Les rejets sont séparée avec précaution de la souche mère et débarrassées
de leurs feuilles jusqu’à une quarantaines de centimètres au-dessus du sol. Les
racines sont également coupée de façon à obtenir un bulbe toute à fait lisse. Les
rejets ainsi préparer sont ensuite mis à sécher à l’ombre pendant plusieurs jours. Ils
peuvent se conserver ainsi pendant plusieurs semaines, à condition de les mettre
encaisse, protégés pas de la paille.
L’emploi de petits rejets de 20 à 25cm, âges de moins de deux mois, est également
fréquent. Ils se préparent comme exposé plus haut. Ces rejets sont cependant moins
recommandables que les grands. Dans les deux cas, on n’utilisera que les rejets de
forme tronconique portant les feuilles étroites et qui donnent de meilleurs rendements
que les rejets à feuilles larges.
On peut également utiliser de veilles souches découpés en morceaux, chaque
morceau ayant au moins un bourgeon. Les surfaces de section sont préalablement
séchées, puis on plante à 20 ou25 cm de profondeur.
La création d’une plantation de bananiers exige une nombreuse main d’œuvre,
estimée au Bas-Congo et jusqu’à l’entrée en production des plants, à quelques 380
hommes/jour par hectare. D’autre part, si l’on n’intervient pas pour maintenir la
fertilité initiale du sol défriché, la durée de l’exploitabilité et de la rentabilité d’une
bananeraie n’est pas très grande. De ce fait, les frais de main-d’œuvre très élevés
risqué de grever fortement l’exploitation de cette plante fruitières »
Source : Van den Abeele, M., Vandeput, R. (1956) Les principales cultures Congo Belge. Publication de la
Direction de l’Agriculture, des Fôrets et de l’Elevage. Bruxelles, Belgique, p 765-779.
b. Factors influencing the quality of Musa planting materials and access to
improved planting material among poor households
1
Yield decline equally affects smaller scale plantations. It is a phenomenon generally determined by soil quality, fertility
management practices and pest and disease pressure. Contrary to small-scale farming systems, however, Musa plant
replacement is an integral part of the production process for export companies and therefore, a calculated expense.
22
The traditional way of planting generally does not acknowledge “invisible” pests and
diseases, such as nematode, viral or fungal infections, leading to empirical plant
sanitation measures which are detrimental in the long run (Hauser, 2007; Jacobsen,
2010). Still, Musa farmers generally do make a distinction between healthy suckers
and unhealthy suckers when planning plantation expansion. Most attention is given to
bunch size and type, plant vigor, leaf health status and absence of weevil galleries.
Farmers may cut off the lower half of the corm of suckers to check for banana weevil
galleries and when galleries are found the tissue is cut out. However, a majority of
farmers use suckers from mother plants with visible pest or disease damage (e.g.
uprooting, broken pseudostem, absence of green leaves at harvest etc; Hauser and
Amougou, 2010).
A compilation of quality criteria from farmers (Cameroon Highlands, Cameroon), in
their own words: “A sucker is healthy if the leaves are fresh and green, preferably
small and lanceolate. There should be about three leaves present and the height of
the sucker should be around 1 m. The base should be wider than the top and have a
diameter of about 20-40 cm. There should be no black spots on the roots and when
you cut the roots, water should flow freely from them. In general a healthy sucker has
many roots and is well anchored in the soil. There should be no traces of weevil
damage on the corm and no ants around the base. If possible it is best to take
suckers from a field where you used pesticides. In summary, a healthy sucker will
prevent you from contaminating your field.
A healthy mother plant is the essence to obtaining a healthy sucker. One can
recognize a healthy mother plant as follows: The pseudostem of the mother plant
should be fresh and thick. When you make an incision in this type of pseudostem, the
water should flow freely. There should be around four suckers at the base, but also
not too many, as this is not a good sign. The leaves should not be yellow and it’s best
not to take a sucker from a toppled mother plant. A healthy mother plant produces big
bunches, and it’s also best if the type of bunch produced is of a marketable variety.
To find out when you need to replace a mat, look at the distance between petioles. If
the distance is far, the mat is still healthy. When the distance becomes shorter, this is
a sign that something is wrong below ground, and it is time to uproot and plant a new
sucker” (Jacobsen, 2010)
Within a country where national extension services are expected to provide
normative guidelines to farmers, great regional variability may be observed in
agricultural practices, including those related to seed management. While such
variation may indicate differences in regional (a)biotic constraints encountered by
farmers, it mostly underlines how fragmented the available information is and
farmers’ dependency on informal learning and word of mouth. Two surveys carried
out in Cameroon, but in separate provinces (approximately 400 km distance),
illustrate such discrepancies at the level of seed management (Table 3). A majority of
farmers applied no treatment to suckers prior to planting and farmers that did, used
one or a combination of treatments with variable levels of efficacy against (a)biotic
constraints.
Table 3: Comparison of regional differences in the % of farmers that applied sucker
treatment before planting
Cameroon Highlands
Southern Cameroon
Applied treatment before planting
20%
Of those that treated (recalculated for Hauser and Amougou, 2010):
Ash coating
56%
Trimmed roots
24%
Pesticide at planting:
38%
Paring
6%
Hot-water treatment
5%
9%
89%
89%
44%
0%
0%
Source: Cameroon Highland survey data – Jacobsen (2010); Southern Cameroon survey data recalculated from Hauser and Amougou (2010).
23
In Nicaragua few Musa farmers pared their planting material before planting. More
farmers were aware of the technology, however, only 23% used it. This was primarily
due to the labour requirements (Gavilan and Martinez, 2000).
Add more non-African references here?
c. Factors influencing quality of Musa planting materials and access to improved
planting material influenced by gender
Karamura et al., (2004) describe the traditional practices of banana growers in
Uganda as follows: “Traditionally, women have always been in charge of banana
groves and this takes up most of their time. They travel long distances towards the
end of the dry season to collect planting materials from far relatives and friends; This
would assure them of probably picking materials which would be pest free since they
were from a different location and the materials would be different genotype to
increase diversity so as to cater for the different needs. The situation seems to be
changing in that farmers pick planting materials from their own gardens these days
for reasons, which are not well understood. Successful management and
maintenance of banana groves in Uganda was thought to be due to careful
implementation of a number of traditional practices to be carried out by women.
There were two types; those connected to the crop, and those controlling the natural
resource base. Those connected to the crop involved; garden location and
composition; sucker preparation and planting; de-suckering; de-belling and detrashing”.
In Kenya where banana is also traditionally an activity carried out by female members
of the household, higher adoption rates of tissue-culture banana technology were
seen for households that are predominantly male-headed, with better-educated and
older farmers (Kabunga et al., 2011a). Similarly Jagwe et al. (2013 – submitted),
found a positive relationship between male-headed households and adoption of
tissue culture technology. It is possible that male-headed households have more
access to credit or labour.
By contrast, Wambugu (2004) states that tissue-culture banana technology has
allowed women-controlled incomes to increase: “There is a more egalitarian
distribution of power as production systems become more market-oriented. The
economic empowerment that comes through the improved harvests and groupfacilitated marketing, raises the self-esteem of the rural farmers (especially women
farmers) giving them the boldness to exercise their constitutional rights when voting
or contributing in group farming activities. In the case of bananas, when the incomes
from the tissue-culture banana farming increase, what used to be a woman activity
becomes a major family activity, as it becomes a bread winning activity. In managing
the banana enterprises together, it brings about family cohesion. Even when men,
who were previously retired and idle, joined the women in the production of bananas,
the women have retained equal control over the income”. Likewise, Ogada et al.
(2010) demonstrated a negative relationship between households headed by males
and the adoption of tissue culture. The dominance of women in banana production as
well as their need for risk-reducing technologies makes tissue culture attractive for
women (Wamue-Ngari and Mwangi, 2008).
In Central America (Costa Rica and Panama), parents provide the majority of
planting materials to persons starting their cultivation activities. Most Musa farmers
are married men. They will stock their farm initially with plants obtained from their
fathers’ farms, but fill in extra and usually minor varieties, first from their wives’
families, then grandparents, aunts and uncles, siblings, and cousins in descending
order of significance. Between 57-94% of Musa planting materials are obtained in this
way. By the time a man is thirty he is likely to have obtained almost all varieties of
Musa spp. available in the area, through further exchange of varieties among
neighboring farmers (Johannessen, 1970).
24
Are there any Asian and more recent Latin American references concerning gender
that could be added here?
VII.
Socioeconomic factors related specifically to access to planting materials
among small holders
a. Supply and demand studies
The maintenance of a small-scale Musa plantation is usually feasible using own
planting materials, occasionally augmented by donations from neighbours or family.
As a consequence, very little trade is seen in conventional suckers, especially where
small-scale farmers are concerned. Few reports could be found in the literature
describing sucker trade markets. In one such study, traders of conventional suckers
in Rwanda and Burundi cited low market opportunities as a major constraint. Other
constraints were linked to pests, diseases and perishability of the suckers.
Suggesting that if market opportunities were better developed, management of
sanitary quality and logistic issues would come to the forefront (Ouma et al., 2011).
Interviews with Central American Musa farmers in the 1960s showed that they
generally give suckers to each other free of charge when needed. Only 2% of the
transactions in planting material were via barter or associated with monetary
remuneration. Such donations and interdependency of farmers on each other’s’
planting materials can be seen as insurance against future unforeseen shortages
(Johannessen, 1970).
Despite the fact that farmers traditionally obtain free sword suckers and contrary to
the apparently low market opportunity for conventional suckers, several studies have
reported farmer willingness to pay for improved planting materials, however, such as
micro- or macropropagated plantlets. In Kenya, over the past decade, multiple
projects were launched, heralding the benefits of tissue-culture technology for smallscale farmers. In the light of demonstrated superiority of tissue-culture banana,
farmers were willing to pay for the tissue-culture plantlets whose cost ranged from 12 US$. The main constraint for farmers to obtain the tissue-culture plantlets was
found to be a convenient supply (Wambugu et al., 2000). Likewise, a household
survey in Nigeria and Cameroon revealed that farmers were willing to pay a higher
price for macropropagated plantlets, under the condition that genetic and sanitary
quality was guaranteed (Wendelboe and Göransson, 2006).
Demand fluctuates: in absence of irrigation, seasonal planting of rain-fed plantains
results in high demand for plants in certain seasons and little demand in others. As a
result, nurseries remain idle in the off-season (Lefranc et al., 2010). Sales
transactions of plantlets from macro- and micropropagation nurseries in Africa often
remain within the context of plantlet-distribution projects run by NGOs and thus
strongly dependent on donor funding. Nursery contracts with NGOs or government
agencies are sometimes financed based on the number of plantlets produced,
without specifications on quality (cultivar, plant vigor, uniformity and presence of
nematodes). In such a scenario, it is the nurseries that benefit most from the project1
(Lefranc et al., 2010; Dubois et al., 2013 – in press).
Nevertheless, in many countries tissue-culture enterprises have been able to develop
profitable businesses. For example in India, a country that accounts for 1/5th of global
Musa production destined primarily for domestic consumption (Arias et al., 2003), a
significant increase in production and productivity of Indian Musa farms has been
attributed to the adoption of improved production technologies, including the selection
of planting material, the adoption of cleaning technologies (paring, pesticide
application) and, under certain management regimes, tissue-culture propagation
(Sundararaju, 2000). IndiaMART.com, India's largest online business-to-business
1
Propagation nurseries financed by the PRFP project in Cameroon received sums ranging up to 30 million CFA,
equivalent to almost 70 thousand US $ (Lefranc et al., 2010) – many nursery owners were not funded for the plantlets
they were contracted to produce, however. This severely jeopardized the quality of the plantlets, as nurseries cut back on
quality control measures (Wendelboe and Göransson, 2006)
25
marketplace for small- and medium-size businesses, lists 43 companies1 selling
tissue-culture plantlets. One such company, Jain Irrigated Ltd2, has pioneered tissue
culture of ‘Grande Nain’ since 1994-95, selling over 2 million plantlets. They are (selfdeclared) the largest banana tissue-culture laboratory in the country (Jain, 2013).
India currently has a production capacity of 40-80 million plantlets per year; 900
million plantlets would be needed to bring 1/3rd of the banana production under
tissue-culture cultivation (Singh et al., 2011).
In Australia, tissue culture technology was available for many years, but increased
demand was seen for the first time after the devastation of the Australian banana
industry by cyclone Larry in 2005-06. The high demand for planting material was only
possible using tissue-culture technology, in the framework of the Quality Banana
Approved Nursery (QBAN) scheme. The QBAN scheme enabled the strategic
production of planting materials necessary to reestablish plantations, both backyard
and commercial (www.abgc.org.au in Singh et al., 2011).
Cuba also represents an interesting case study, given the recent developments in
commercial enterprise. In 2000, for example, Cuba had an annual production of 2030 million tissue-culture plantlets produced by “Biofabricas”, of which there were 12
units distributed throughout the country (Lescot et al., 2000).
In 2004, Arab countries produced 1.9 million tons of banana, 34 000 tons of which
were produced in the Sultanate of Oman (AOAD, 2005). The total cultivated area of
banana in Oman reached 2,600 ha in 2005, whereas, the production of banana grew
rapidly from 10 000 tons in 1970 to 34 982 tons in 1984 when it reached its highest
level. Production then fell to 22 100 tons in 1988. Since 1989, its growth has been
steady, leveling out at 25 955 tons in 2006 (Al-Hosni et al., 2010). In 1995, the
production and dissemination of tissue culture plantlets of the cultivar Williams was
initiated to encourage banana cultivation. The laboratory was set-up under the
auspices of the Ministry of Agriculture and Fisheries, together with the University of
London (Viswanath et al., 2000). This project was apparently successful in boosting
local production and demand for tissue-cultured plantlets has risen. National
production was not increased to meet this demand, however, and Oman now
frequently imports tissue-culture plantlets from Jain Ltd (Jain, 2013).
Constraints to the development of tissue-culture technology in East Africa concern
mostly adoption (demand) or production (supply) issues. Wambugu et al. (2000)
identified the following bottlenecks for the dissemination of tissue-culture technology
in Kenya: lack of quality control, lack of research and technology for backstopping,
lack of diagnostic facilities, price harmonization, lack of information about market
characteristics to avoid exploitation by middlemen and poor linkage between farmers
and tissue-culture labs. Burkhart (2009) identified similar problems between tissueculture producers and nurseries, and some additional issues during a survey of the
40 tissue culture nurseries in Burundi, Kenya and Uganda, namely, bad timing, poor
quality and insufficient quantity of plantlet supply. At the nursery level, water access,
credit, and transport of plantlets proved problematic (Burkhart, 2009).
Efforts have been implemented to amend some of these constraints by introducing
facilities to provide credit, information, complementary inputs, infrastructure
investments and marketing networks. However, progress remains marginal and
strategies must be tailored specifically to local conditions. For example, a cost-benefit
study in Uganda revealed that the use of tissue-culture plantlets was increasingly
more profitable than suckers with proximity to the main banana market. In districts
further from the main banana market, however, farmers could receive similar gains
by planting suckers than tissue-culture bananas. The same trend of diminishing
returns for tissue-culture plantlets, compared to suckers, with distance from the main
banana market was observed in Burundi and Kenya, although no quantitative cost-
1
Nine of the country’s TC labs are recognized by the NCS/TCP initiative of the Department of Biotechnology, Government
of India.
2
http://www.jains.com
26
benefit has been conducted (Dubois et al., 2013 – in press). Such findings reflect
those of Wairegi and Van Asten (2010), who determined that fertilizer application was
only profitable for Musa farmers within a 160-km radius around Kampala. Similar
regional variation is seen in Kenya, farmers in high-potential banana areas are less
likely to adopt tissue culture, as bananas grow relatively well, even under poor
management, resulting in less need for tissue-culture bananas. So, the technology
should be geographically targeted, and the spatial variation of banana yields and
constraints, and of input and output prices, should be considered (Kabunga et al.,
2011b; Jagwe et al., 2013 – submitted).
In Burundi, Kenya and Uganda, drivers for successful nurseries were close proximity
to both the producers of tissue-cultured plantlets and the market they wish to serve.
Good agricultural practice was also important and diversification into crops other than
banana (Burkhart, 2009). Tissue-culture nurseries are sometimes run independently
from tissue-culture producers in Kenya, and often owned by formalized farmer groups
that equally act as customers for these nurseries. Such a business model may hold
the secret for a sustainable link between tissue-culture producers and farmers
(Dubois et al., 2013 – in press).
The development of a reliable demand of Musa planting materials is a delicate
exercise, considering the traditional lack of such a market. The Maendeleo
Agricultural Enterprise Fund1 describes the creation of demand for tissue-culture
banana plantlets in Kenya as follows: “a viable commercial unit (farm ed.) requires on
average 80 tissue-culture banana plants. With the average cost of the tissue-culture
materials being $1–$1.2 per plantlet, a viable commercial enterprise requires 80
plantlets with a capital investment of US$ 100 on purchasing plantlets alone. Many of
the farmers can afford only a few (5-10) plants; too little to impact on poverty
alleviation, thus the need to provide them with credit to increase their adoption levels.
This project therefore had to help farmers in the target area in accessing micro-credit
to enable them to establish viable commercial units of banana orchards, a mission
that was made possible through partnerships with Rural Credit and Finance
(RUCREF-Ug), MBD and K-REP”.
A survey of Musa seed systems in Asia and the Pacific showed that tissue-culture
plantlets are sold commercially and used by medium-scale (60% use tissue-culture
plantlets) and large-scale (90%) farms in Asia and the Pacific, namely in Australia,
Philippines, India, Indonesia, China, Malaysia and Taiwan. In these countries
production is either for export or for a large domestic market (China and India). Other
countries in Asia and the Pacific (Thailand, PNG, Cambodia, Vietnam, Pacific
community, Bangladesh) have tissue-culture plantlets available through research
institutions or universities, but only for research purposes. Small-scale farmers in
Asia and the Pacific rarely use micropropagated plantlets (Molina et al., 2011).
Reasons cited by farmers in Asia and the Pacific for not using micropropagated
plantlets included: high cost, lack of knowledge of the technology, frequent
observation of off-types and absence of commercial micropropagation facilities in the
country (Molina et al., 2011; Langford et al., 2012). For example, in Thailand, a
government scheme was set up to improve the production and management of Kluai
Khai (the nation’s 3rd most important cultivar) by smallholders. The Ministry of
Agriculture provided government grants and technical support to increase
sustainability and competitiveness of agricultural cultivation. Farmers rejected the use
of tissue-culture plantlets due to their price and management requirements
(Wattanachaiyingcharoed, et al., 2000). Where farmers have suffered BBTV losses,
however, improved planting materials are more readily accepted. For example, in the
Philippines where several delivery schemes were developed (Molina, 2004),
sustainability of the projects has been fostered though partnerships between NGOs
and private tissue-culture facilities.
1
http://www.maendeleo-atf.org/Project-Profiles/profs_isaaa_4.html
27
In Costa Rica, beginning in the mid-1980s, adoption rates of tissue-culture banana
technology were greatest among export banana farmers, for whom distribution
channels are consolidated and institutionalized, supported by Banana Corporation,
CATIE, the academic laboratories, and private firms. For a small set of farmers,
however, market mechanisms are not enough and non-market ones are not
institutionalized leading to exclusion from the technology and the learning practices
and norms associated with it. By contrast, in Jamaica, tissue-culture banana plantlets
have been available only on a sporadic basis. Larger plantations imported tissueculture bananas in the mid-1980s, while the small farmers have had only limited
access through government research facilities and local farmer co-operatives. Efforts
at local production and price subsidies increased access and use of tissue-culture
technology, however, insufficient capacity and resources rendered efforts
unsustainable. Costa Rican small farmers, on the other hand have been able to
benefit from greater access to tissue-culture technology (Bortagaray and Gatchair,
2012).
Tissue-culture technology1 is both knowledge-intensive and requires considerable
adjustments in traditional practices. Information dissemination is an important
challenge that will influence the demand and adoption potential of tissue-culture
technologies. For example, NGOs and extension agents often demonstrate the
benefits of innovations using well-managed demonstration plots with conditions that
not all farmers can reproduce. On the other hand, through informal channels negative
information can spread faster and more widely than positive information (Kabunga et
al., 2011b).
There is little evidence to suggest that small-scale farmers are currently able to profit
from the benefits of tissue-culture technology without project-mediated support. A
survey conducted by FAO revealed that traditional suckers are used by more than
92% of the growers across the world while approximately only 8% have access to
tissue-culture based planting materials (Singh et al., 2011). So, it appears that
medium- and large-scale producers are better equipped to capitalize on opportunities
provided by tissue-culture technology.
On a more accessible level for small- to medium-scale farmers, and agricultural
entrepreneurs in rural-based economies, the potential of macropropagation to
multiply planting material has encouraged the emergence of a new profession
(nursery man/woman), entailing the production, commercialization and distribution of
clean planting materials to farmers (Temple et al., 2006; Lefranc et al., 2010; Ouma
et al., 2011; Tomekpe et al., 2011). Macropropagation has been successfully used in
Uganda as a method for the rapid multiplication of clean material following a BXW
outbreak (Sengendo et al., 2006).
Macropropagation nurseries are hampered as a small business venture, however, by
the amount of initial investment required. A survey by Wendelboe and Göransson
(2006) in Cameroon and Nigeria showed that the most common source of start-up
capital was from own savings, indicating probable difficulties securing bank loans.
This suggests exclusion for resource poor individuals from entering the plantain
plantlet market and the importance of social networks or off-farm revenue
(Wendelboe and Göransson, 2006). Lack of sufficient corm material, transport
difficulties, skill requirements, lack of training and financial concerns have also been
cited as major constraints in Ghana, Rwanda, DR Congo and Burundi (Wendelboe
and Göransson, 2006; Dzomeku et al., 2010; Ouma et al., 2011). An economic
analysis of banana seed systems using macropropagation chambers in Rwanda,
Burundi and Eastern DR Congo (North and South Kivu), demonstrated that between
47-77% of the chambers operated with loss. At the time of the survey, the majority of
the institutions were producing banana plantlets to distribute to farmers free of cost
and both the set up and running operations were entirely dependent on funding
support. Constraints cited by suppliers of Musa plantlets in Central Africa focused
1
The fragility and extra care requirements necessary for macropropagated plantlets, suggest similar adoption constraints
related to information dissemination, as those encountered for micropropagation.
28
either on construction and maintenance or lack of market opportunities and technical
problems (Ouma et al., 2011). Other limiting factors include temperature-dependent
productivity (sub-tropical and tropical highland regions are not ideal) and the need to
find an alternative to firewood, as the amounts required during boiling water
treatment of suckers and sterilization of media may negatively impact environmental
sustainability and wide scale adoption by resource-poor farmers (CIALCA, 2012).
A comparative overview of the cost price for the construction of a macropropagation
chamber and its employment for 1 year in several African countries is given in Table
4. Total costs are extremely variable (unreliable?) between studies, but consistently
lower compared to tissue-culture1 (Danso et al., 1999; Njukwe et al., 2007; Ouma et
al., 2011)2.
Table 4: Comparative cost price for the construction of a Macropropagation chamber
(US $)
Location
Cameroon Uganda
Rwanda
North Kivu
(DR Congo)
Pramkese
(Ghana)
Gyedu
(Ghana)
Propagator
650
490
172
14
36
Size
1,2 x2x1m
6x1,5x1
m
2x1x0,75m
Not
included
Not
included
Materials &
tools
951
3453
1339
41
70
Labour
700
261
108
39
36
Land
Not included
1452 (6
sq m)
484 (2 sq m)
4 (0.1ha)
3 (0.1ha)
Transport
Not included
14
9
4
18
Total
2301
5670
2111
103
163
Source
Njukwe et al.,
2007
Ouma et al., 2011
Danso et al., 1999
Analysis of PRFP3 by Wendelboe and Göransson (2006) estimated that the
implementation of the project disrupted the emerging economies of the
macropropagation nursery business, by (1) donating plantain plantlets for free to
farmers and (2) failing to fund nursery owners for the plantlets they were contracted
to produce.
In fact, the donation of free planting materials is not necessarily detrimental, as long
as certain conditions are met. Firstly, the quality must be guaranteed and result in a
significant and marketable yield increase. Secondly, farmers must be correctly
informed of the labor requirements associated with the new technology.
Households will generally have two sources of uncertainty about these types of
technologies: they may be uncertain about the effectiveness of the product and about
its non-monetary cost of usage (for example, labour). People immediately learn the
cost of usage upon buying into the technology. By contrast, learning about the
effectiveness may take some time. And even though, as in the case of tissue-culture
1
A modest tissue culture facility can cost US$50 000 to equip (Arias et al., 2003).
This price range is tentative: different components were considered in the different studies and cost estimate methods
differed. For example, in the study by Danso et al. (1999), 0.1ha was used in each village and land was considered
inexpensive at all locations since in each case the project was considered as a community enterprise. By contrast, the
study of Ouma et al. (2011), used the opportunity cost of land for a year in sites not too far from the city center which tend
to be highly priced compared to the more remote locations (Ouma, pers. comm.).
3
Dissemination of macropropagated plantlets through formal partnership with NGOs, agricultural projects, producers’
organisations and extension services (Tomekpe et al., 2011)
2
29
technology, yields may increase, they remain susceptible to losses due to factors that
are not related to the technology, such as black leaf streak disease, drought or
fertility-related issues.
Research carried out by Dupas (2010) suggests that subsidies may have no effect on
the adoption of the product if people initially underestimate its non-monetary usage
cost. This is because subsidies affect the purchase decision of households who have
a low prior conviction about the product’s effectiveness. Such households may not
use the product once they learn its true usage cost, however. In this context, higher
subsidies may not generate additional signals about the product’s effectiveness and
therefore may not affect the dynamic adoption process. By contrast, subsidies may
positively affect the diffusion process if people initially overestimate the non-monetary
usage cost (or if they are properly informed).
If done with care, there is no evidence that people will anchor around subsidized
prices indefinitely. Short-run subsidies associated with technologies that elicit higher
returns, may even increase long-run adoption through experience and social learning
effects (Dupas, 2010).
By contrast, the consequences of failing to honor the PRFP contract may have a
significantly negative impact on adoption, by jeopardizing the quality of planting
materials (as contracted nurseries failed to implement necessary quality control
measures). Similarly, giving tissue-culture material (or by proxy macropropagated
plantlets) to farmers who are unaware of the additional care requirements, will
damage the perception and adoption potential of tissue-culture technology (Dubois et
al., 2013 – in press).
The most accessible means for small-scale farmers to acquire larger quantities of
planting materials will be field multiplication methods, such as complete and false
decapitation. The multiplication practices should carefully follow the best practice
guidelines described in Lescot and Staver (2010) in order to minimize the risks of
transmitting pests or diseases.
b. Returns to investment
Although backyard garden systems, subsistence systems and commercial systems
are extremely variable (except the commercial), each has distinct characteristics that
broadly distinguish it from the others. The production technologies used for export
and those used for local or home consumption are, in fact, so different that they can
be considered as distinct economic activities. Although there is much within-group
variation, several general principles can be discerned (Arias et al., 2003; Karamura et
al., 2000):
(1) Production for local markets or home consumption makes limited use of external
inputs, is labour intensive, small (0,25 – 5ha), mostly rural and production costs are
generally low
(2) Production for export markets, by contrast, is technologically sophisticated, from
the selection and treatment of planting materials, seed bed preparation, crop
establishment and stand management (including pest and disease control) through to
marketing and/or processing.
The difference in profit margins obtainable from either production system will
inevitably impact willingness to invest in improved planting materials. For example,
micropropagation techniques allow export banana companies to maintain singlecycle plantations, which are extremely vigorous and have a high yield potential (up to
three harvests), after which they do not appear to show significant differences with
conventional plants. To be profitable, however, much care has to be taken in
transporting the plants from the nursery to the plantation, and the soil needs to be
treated with pre-emergence herbicides. As the plants have low nutrient reserves,
daily fertilization, or ideally fertigation, is required. The high yield potential (up to 120
Mg/ha for Cavendish) requires rigorous soil fertility management and is logistically
demanding at harvest (Arias et al., 2003; Singh et al., 2011). Similarly, the technique
of high density planting, which originated in Latin American plantain plantations, also
requires the use of large quantities of highly uniform planting materials (e.g.
30
microcorms or other methods of macro- and micropropagation). Yield potential of
high-density plantain plantations of 78 Mg/ha have been recorded (Belalcazar et al.,
1994; Rosales et al., 2010).
An illustration of the range of prices cited for different types of Musa planting
materials around the world is given in Table 5.
Table 5: Comparative cost of Musa planting materials (US $)
Country
Untreated
Brazil
0,15
Jamaica
0.15-0.30
Treated
Micro-corms
Macro-
suckers
Micro-
Source
propagation
Oliveira de
almeida et al.,
2000
1.00
0.40 (EU
subsidized
price)
Cameroon
0,04-0,08
Cameroon
0.20
0.29-0.46
Ngo-Samnick,
2011
Cameroon
0,10-0,20
1,4
Hauser, pers
comm.
0,54-0,60
Ouma et al.,
DR Congo,
Rwanda,
Burundi
Ghana
0,09-0,12
0,20
0,40
0,66
Purchase
price
Lefranc et al.
2010
2011
0,60
0.05-0.06
0.13
Kenya
Farmers’ own
valuation
(labour cost)
0,80-1,00
Bortagaray and
Gatchair 2012
1.18
(current
price)
0.12
0.160.190.251
Tanzania
1.5 euro
(2002)
India
0,87
Qaim (1999a)
0.41 (price
at DuRoi
SA)2
0.12-0.94
=>Smallmediumlarge farmers
(implicit
price)
Danso et al.,
1999
0,02
10 euro
(1996)
Gallez et al.,
20043
1,05
Singh et al.,
20114
By contrast, African farmers face some of the highest transaction costs in integrating
themselves in the marketplace, paying 3 to 5 times the world market prices for inputs,
while receiving only a fraction of market value for their produce (Simpson, 2006).
1
Small farmers purchase less frequently, so average sucker cost is cheaper than for larger farmers who depend more on
purchased suckers (Qaim, 1999). This is an inverted relation compared with seed propagated crops, where poorer
farmers often have to purchase seed, compared to richer/larger farmers who have enough left over to replant at next
planting season, Almekinders (2000)
2
A direct comparison is difficult, e.g. different growth stage of plantlet at selling time – but gives an indication that there is
room for further price reduction as business competition (or economies of scale) have effect (Qaim, 1999a)
3
For suckers of improved cultivars, originally from in vitro derived, but eventually multiplied by farmers as a by-product of
normal cultivation or in rapid multiplication plots (Gallez et al., 2004)
4
Calculated as cost price per bunch (Singh et al., 2011)
31
Returns associated with the use of tissue-culture banana in Kenya include improved
food security, nutritional levels, economic status of the rural poor, and provision of
cash income security (Acharya and Mackey, 2011; Mbogoh et al., 2002; Njuguna et
al., 2010a). On average, small-scale farmers harvested bananas with a bunch weight
of more than 40kg compared to the usual average of 15-30Kg (MOA, 1994 in
Wambugu et al., 2000). An ex ante analysis of potential benefits for Kenyan farmers
estimated that the average per acre incomes for small, medium, and large-scale
farms would rise by 156, 145, and 106 % respectively, if tissue culture banana
plantlets were used in combination with the more intense management package
(Qaim, 1999b). Farmers with lower than average yields are more likely to adopt
tissue culture. Controlling for this negative selection bias, an ex post household
survey, demonstrated a positive and significant tissue-culture net yield gain of 7% - if
irrigation had been used, an estimated 20% yield gain might have been achieved, as
observations were made during a year with exceptionally low rainfall. In a two-year
survey of the same households – including one year with and one year without
drought – a yield gain of 50% was found. Yield gains may improve more under the
condition that farmers apply optimal management (Kikulwe et al., 2012). Among the
tissue culture adopters, labor use and the application of inputs such as fertilizer and
water are still quite low, however (Kabunga et al., 2011b). This suggests that
extension efforts to deliver the technological package to smallholder farmers should
be scaled up (Kikulwe et al., 2012).
In Jamaica, banana production is seasonal and variable. In adverse weather
conditions domestic market prices are more favorable than export prices and vice
versa. As a result it cannot be stated categorically that export farmers who have
access to tissue-cultured material, will have higher returns on their investment
compared to small farmers who supply the domestic market. However, export
farmers generally have more options available and are able to capitalize on price
fluctuations, and therefore more likely to have a steadier income stream (Bortagaray
and Gatchair, 2012).
Boiling water treatment is probably the most accessible option to obtain clean
planting materials (Hauser, 2007), with high returns on investment. It has been
demonstrated that plant growth is usually faster, more plants produce an edible
bunch, and bunches are heavier in field plots established with suckers that have
been immersed in boiling water compared to control plots. Additionally, sucker
sanitation induces faster crop cycling, reducing weeding requirements, so that fields
can return to fallow or other crops earlier (Tenkouano et al., 2006). Paring is timeconsuming, between 1-3 minutes is required per sucker. However, paring allows an
additional level of quality control – for example, weevil galleries become visible. This
is especially important, because the heat of boiling-water treatment does not
penetrate into the heart of the corm, where weevil larvae may survive. In combination
with sucker multiplication plots, however, farmers’ groups could produce sufficient
planting material with very little additional investment requirements (Table 6).
Although demonstration plots are required to convince most farmers that paring and
heat treatment will not kill the suckers. Total labour requirements and capital and
operational costs are summarized in Table 6 (Hauser, 2007).
All technological innovations for the improvement of Musa seed systems will require
an initial monetary or labour investment on the part of the farming household. Even
though the investment may be returned many times over at the time of harvest,
resource poor households must choose whether to engage or not to participate. Riskdiversification is a common strategy for poor households and even though most rural
families are involved in agriculture, it is rarely their sole occupation. Temporary urban
migrations or off-farm activities to complement farm revenue can provide families
some insurance against crop failure. Risk limiting strategies may also include
conservative management of farms and businesses. So, even though a technology
may prove to be beneficial in the long-run, the experience of living in a high-risk
environment, often dictates a preference for traditional cultivation practices (Banerjee
and Duflo, 2011). Choosing to invest in clean planting technologies, translates as
32
less resources for other economic activities. This opportunity cost will also play a role
in the success of adoption.
Table 6: Labour requirements and capital and operational costs for 1 ha of different
plantain sucker-sanitizing procedures at Nkolmetet, southern Cameroon.
Control
Nematicide
Ashcoating
Hot-water
Boiling-water
Paring
60
66.5
62.5
85.6a
70.8 b
Non-paring
0
6.5
2.5
25.6a
10.8 b
Capital
0
0
0
63c
10d
Operation
0
430
0
10
0
Labour (person
hours)
a: Four persons conducting hot-water treatment; b: Two persons conducting boiling-water treatment; c: 10
% depreciation; d: 50 % depreciation (Source: Hauser, 2007)
VIII.
Institutional factors
a. Policies and regulations related to seed
On an international level, several guidelines and protocols exist related to Musa
planting materials. National import and export regulations for seed and other planting
materials have been developed for most countries under the International Plant
Protection Convention (IPPC), an international plant health agreement, established in
1952, that aims to protect cultivated and wild plants by preventing the introduction
and spread of pests. FAO, as the depository of the IPPC, has a mandate to assist its
member governments to strengthen their plant quarantine services, while Bioversity’s
mandate, among others, is to further the collecting, conservation and use of the
genetic diversity of useful plants, including Musa, for the benefit of people throughout
the world.
The Second Report on the State of the World’s Plant Genetic Resources for Food
and Agriculture (FAO, 2010) emphasizes the need in many countries to develop
national policies and legislation related to the conservation, exchange, and use of
plant and genetic resources for food and agriculture (PGRFA), including
phytosanitary regulations. Overall, most countries have enacted or revised national
legislation dealing with PGRFA issues including breeders’ rights, biosafety,
intellectual property rights, phytosanitary aspects, seed systems, access and benefit
sharing, and Farmers’ Rights. There are also ongoing efforts to harmonize seed laws
across regions, particularly in Africa and Europe. At the international level, the entry
into force of the International Treaty on PGRFA in 2004 to promote conservation and
sustainable use of PGRFA and the fair and equitable sharing of the benefits arising
out of their use, is probably the most significant development1.
A process comparable with the certification seen for seed propagated crops, was first
developed for Musa in the early 1980s with the advent of tissue-culture technology.
Since then, micropropagation in combination with third-country quarantine2 and virusindexing have been used for the safe exchange of Musa germplasm and represent
1
The International Treaty on Plant Genetic Resources for Food and Agriculture (ITPGRFA) includes Musa as one of the
64 crops in the Multilateral System. The Multilateral System incorporates the concept of Access and Benefit Sharing
stipulated in the Nagoya Protocol to the Convention of Biological Diversity.
2
Countries without stations may allow entry of items that are exempted from prohibitions after passage through
intermediate or third-country quarantine. Under third-country quarantine, a country imports high risk material from another
country but the material first goes through quarantine in a third country. The first two countries are usually in the tropics or
sub-tropics, but the third country is usually in a region with temperate climate. The third country may accept the risk
because the crop is not grown there; the organisms have narrow host ranges and are not likely to attack crops in the third
country, or the organisms are not likely to become established because the environment is unfavorable (Committee on
Managing Global Genetic Resources: Agricultural Imperatives, National Research Council. "11. Exchange of Genetic
Resources: Quarantine." Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC:
The National Academies Press, 1993).
33
the international standard for movement of Musa germplasm (Vuylsteke, 1989;
Diekmann and Putter, 1996). Where tissue-culture is not possible, full quarantine
measures are advocated until the vegetative material can be cultured in vitro. Virus
indexing procedures and results should be carefully documented, e.g. in a
germplasm health document, to enable certification that the germplasm is free of all
known Musa viruses. Technical protocols for the collection and preparation of
vegetative planting material for international movement are described in detail in
Diekmann and Putter (1996).
Bioversity’s International Transit Centre (ITC), functions as a third-country quarantine
and is the world's largest in vitro collection of Musa spp. Kept under the auspices of
FAO and located at the Katholieke Universiteit Leuven (Belgium), the ITC was
established in 1984. The ITC conserves banana accessions 'in trust' for the global
community. An average of 6 accessions are sent daily to researchers and growers
around the world. To date over 8000 accessions and 90,000 samples have been
dispatched to 359 different locations in 103 countries. Since the mid-1990s,
accessions in the international collection are tested for banana viruses in three
globally recognized virus indexing centers: QDPI (Australia), CIRAD-FLHOR (France)
and PPRI (South Africa; Garmin et al., 2010).
The first true certification scheme for bananas was developed in Australia in the mid1990s. The Banana certification scheme established by the Queensland Department
of Primary Industries is used as the fundamental management tool for the control of
BBTV in Australia, and has been adopted in several other countries where the
disease is a major problem. According to this system, banana plants (excluding fruits)
must not enter Queensland without an Inspector’s Approval, unless the plant is, a)
banana tissue-culture plantlet, b) is in a sealed pest proof container, c) is
accompanied by either a QBAN certificate for the plant or an inspector’s certificate
stating the plant may be introduced, and (d) is transported in a way that prevents
infestation by a banana plant pest (Singh et al., 2011).
In India, the Department of Biotechnology (DBT), Government of India in
collaboration with Indian Council of Agricultural Research (ICAR) and Ministry of
Agriculture have developed standards for banana tissue-culture and also for
assessing tissue-culture facilities. DBT has launched the National Certification
System for Tissue-culture raised Plants (NCS-TCP) under which a number of
Accredited Test Laboratories (ATLs), including some for virus indexing and genetic
fidelity testing. The ATLs certify the planting materials using standards approved by
the Ministry of Agriculture. Increasing awareness has resulted in farmers who now
insist upon certified plants from their supplier (Singh et al., 2011).
Despite the rigor of the formal process described above, quality problems may creep
in (Vuylsteke, 1998; Vezina and Dubois, 2012):
(1) Biological problems may arise for micropropagated plants (blackening of the
explants, contamination of cultures, culture deterioration or loss of genetic integrity
through somaclonal variation)
(2) Virus indexing schemes are still largely absent in regions where
micropropagation is currently being promoted to small-scale farmers, e.g. East Africa.
Indeed, in many regions, one of the biggest challenges for the sustainable
commercial development of a formal Musa seed system using micropropagated
plants is, in many regions, the lack of several essentials: (1) standards for quality
management during the production process, (2) plant health certification, (3) tissueculture producers’ access to virus-free and true-to-type mother plants through the
establishment of certified mother plant gardens and (4) regulatory procedures
(Dubois et al., 2013 – in press; Vezina and Dubois, 2012). Creation of awareness of
quality plants through vegetative propagation especially using suckers,
macropropagated plantlets and tissue-culture plants is important for farmers as well
as industry (Singh et al., 2011)
Some steps have been taken to amend these problems. For example, Bioversity
International and CORAF/WECARD officially recognize CARBAP as the regional
center for multiplication and diffusion of in vitro propagated banana plants in West
34
and Central Africa. Proliferating plant tissue is obtained from certified genetic material
coming from the ITC and within the framework of national and regional projects,
CARBAP provides indexed tissue-culture plantlets from which the national institutions
can initiate in vivo mass-propagation. Nearly 50,000 tissue-culture plantlets have
been distributed in the past 15 years (Tomekpe et al., 2011).
Similarly, in Asia and the Pacific, regional cooperation plays an important role.
Countries like Australia, India, Taiwan and China have well developed virus
diagnostic and fidelity testing systems. BAPNET (Banana and Plantain Network for
Asia and Pacific) and Bioversity have been working on the rationalization of Banana
Virus Indexing protocols at global and regional levels in collaboration with Australia,
India and the Philippines. This network can now offer training on fidelity testing and
virus indexing to other Asian countries (Singh et al., 2011).
National regulations concerning Musa planting materials: what major differences are
there between countries or between regions, in content or ability to reinforce
regulations? Are national quarantine authorities in contact with international networks
that can facilitate training and capacity building?
The absence of formal plant certification schemes is not necessarily problematic, as
high quality may be maintained under optimal management and in absence of legal
recognition. There is, in fact, a movement in industrialized countries towards quality
declared seed, where quality is maintained without regulation. And, although
improved quality can be imposed through legislation, self-imposition of standards by
industry and farmers may yield even better dividends (Bentley et al., 2011).
The Quality Declared Seed System, presented by FAO in 1993 and revised in 2006,
serves as a quality assurance scheme for seed production. For vegetatively
propagated crops, the FAO issued production protocols and standards for quality
planting material in 2010, “FAO Quality Declared Planting Material (QDPM)
guidelines”. While these guidelines fall legislatively short of the certification process,
they must comply with national seed regulations and provide a set of protocols and
standards allowing the verification and monitoring of the production and distribution
process (FAO, 2010). It is less demanding than full quality control systems and, thus,
can be more easily implemented in situations where resources are limited (FAO,
2006).
The risk of transmitting seed-born pests and diseases varies depending on the
multiplication method used (Table 2). The information presented in this table is not
supported by survey or experimental data, but relies on expert opinion of most likely
scenarios.
Table 2: Relationship between sanitary quality and multiplication method
Pest/disease
Suckers
from field in
production
Suckers in a
multiplication
plot
Microcorms
PIBS
Tissue
culture
Bacterial diseases*
BBTV*
BSV
Other viruses
Foc*
Nematodes
Weevils
2
2
1
2
2
1
1
1.5
1.5
1
1.5
1.5
1
1
1
1
1
1
1
0
0
2
2
2
2
2
0
0
0.5
0
2
0.5
0.5
0
0
0 = zero risk; 1 = low risk; 2 = moderate risk; 3 = high risk
Source: Karamura and Staver (2010)
The above table would benefit from confirmation through experimental data.
For Musa suckers (or any derived planting material) destined for international
transportation, especially from tissue-culture, the following quarantine diseases
35
should be absent from country of origin: Moko disease due to Ralstonia
solanacearum Smith, phylotype II; Xanthomonas wilt caused by Xanthomonas
vasicola pv. musacearum; Tropical Race 4 Fusarium oxysporum var. cubense;
BBTV; BBrMV. For planting material destined for local or within country sale or
exchange, the above diseases should be completely absent from the field and all
surrounding fields. The farther these diseases are from the source of the planting
material, the lower the risk of contamination of the seed material (Lescot and Staver,
2010). Guidelines for the production of quality declared planting materials are
described extensively in Lescot and Staver (2010).
b. Public and Private stakeholders, partnerships and linkage with the informal
system
A clear-cut distinction between the informal and formal seed system does not exist in
situations where public or private institutions are engaged in the production of
uncertified, unlabeled or registered seed lots (Almekinders, 2000). Informal seed
systems can also serve as channels for the diffusion of improved varieties, through
linkage with the formal seed sector (Thiele, 1999).
Numerous examples of linkage between the formal and informal systems exist for
Musa. A case in point are the National Repository, Multiplication and Dissemination
Centers (NRMDC) launched in 2000 by BAPNET to meet the need for high-yielding,
pest- and disease-resistant cultivars in Asia and the Pacific. Serving as relay centers
to the Musa ITC, their main objectives were identified as follows: (1) to improve
access to new hybrids and superior varieties from INIBAP; (2) local multiplication to
provide materials to national programs for more expanded evaluation activities; (3)
local multiplication to provide materials for the eventual adoption by farmers; and (4)
to maintain disease-free foundation stocks (Van den Bergh et al., 2004). The
NRMDCs are integrated in the evaluation and promotion of improved varieties as a
national activity and supported by national resources, although the level of support
provided has been variable between countries. In the Philippines and Sri Lanka,
national funding has enabled the NRMDCs to carry out more expanded field trials
(Molina, 2004). Yet, the capacity of the NRMDCs in some countries has been too low
for the supply of materials on a large scale. In the Philippines, cooperation between
the NRMDCs, government institutions, private companies and NGOs has made a
delivery system for small-scale farmers feasible.
Ten years on, the centers are deemed partially successful. They served mainly to
create opportunities for BAPNET partners to intensively evaluate cultivars of regional
interest. For example, NRMDCs included Foc resistant somaclones from Taiwan,
which were evaluated and adapted by countries experiencing Tropical Race 4
problems. NRMDC was also the platform used to initiate adoption of
micropropagation for clean planting materials. A delivery system was developed to
provide affordable and accessible seedlings to small-scale farmers (Molina, pers.
comm.).
Questions:
How well were the NMRDCs funded in participating countries? How are they doing
now (ten years on)? Do they have a continuing role to play or did they address an
urgent need? Have these programs been integrated in national priority agendas? If
not: why not? What can be improved? How instrumental were the NMRDCs for the
uptake of tissue-culture technology in the region? For example, would countries as
India and China have taken up tissue-culture technology anyway? What role did
NMRDCs play (did they jump on a bandwagon or help develop the bandwagon)?
For small-scale Musa farmers, linkage between the formal and informal systems is
found mostly in the form of technology transfer projects run by stakeholders of the
formal system (NGO’s, research centers, government bodies, private tissue-culture
laboratories). Nweke et al. (2011) coined the term “semi-formal system”, to describe
the dissemination of Musa planting materials by NGO’s to farmers, who then multiply
36
and redistribute following traditional practices of the informal system. This semiformal set-up is often explicitly included in the structure of technology transfer
projects, in the form of mother-baby plot experiments1 (e.g. the INNOBAP2 project).
The NGO’s source the planting materials from research centers or subsidized tissueculture laboratories.
Numerous national, bi- or multilaterally funded projects have targeted improvements
for Musa seed systems through public-NGO partnerships. Local and elite cultivars or
hybrids have been multiplied and distributed to smallholders, in Africa, Asia, the
Pacific and Central America (Table 7). Project variables include the price of plantlets
(free, subsidized or full price), involvement of the private sector, the multiplication
technique used (conventional suckers, macro- or micropropagation), composition of
the technology transfer package (local or elite cultivars and hybrids, transfer of
multiplication technology, clean planting technologies), and development of
institutional support (advice, micro-credit schemes, subsidies, partnerships). These
projects have been met with variable degrees of success and their reports are riddled
with hypotheses about the long-term sustainability of the introduced technologies.
Impact statistics are based mainly on the number of plantlets distributed and the
number of farmers implemented or trained. Where adoption studies have been
carried out, the definition of “adoption” is not always clear. Is an adopter somebody
who agreed to participate in the project or somebody who will continue with the
technology regardless of subsidies and technical assistance provided through the
project? And how can we evaluate adoption when fundamental problems concerning
infrastructural support (sanitary regulations, quarantine mechanisms and production
facilities) are not guaranteed beyond the lifetime of the project?
For example, considering Kenya as a whole, 5,2% of the total banana area is
currently under tissue culture cultivation, representing an estimated 6% of banana
farmers (Njuguna et al., 2010b). In Central and Eastern Provinces, where most of the
dissemination programs started, adoption rates are around 15% (Kabunga et al.,
2012). Kabunga et al. (2012) define adoption as “the use of at least a few TC
plantlets by a household”. However, purchase prices are subsidized and use of the
entire technology package is not considered in the definition of adoption, even though
the absence of improved management practices will have adverse effects. Under
sub-optimal agricultural management practices and disease pressure, Vuylsteke and
Ortiz (1996) demonstrated no superior horticultural performance from tissue-cultured
plantlets. A similar lack of improved agricultural practices under drought stress, found
more than 68,9% plant loss for macropropagated plantlets, compared to 46,8% loss
for traditional suckers and 21,4% for boiling-water treated suckers (Mekoa and
Hauser, 2010).
To date, no rigorous studies are available describing ex post socio-economic benefits
or long-term adoptive success of the transferred technologies for any of the projects
listed in Table 7 (confirm this). For East Africa, for example, only anecdotal
evidence can be found of benefits to farmers, partly because of a large body of
subjective ‘grey’ literature, sometimes unconditionally and unilaterally promoting the
benefits of the tissue-culture bananas (Dubois et al., 2013 - in press). Some notable
efforts have been made recently to amend this situation (e.g. Kabunga, 2011b;
Kikulwe, 2012).
1
Mother and baby trial design layout: A mother trial is centrally located in a village or at a nearby research station and
replicated on-site. Baby trials are located in farmers’ fields and compare a subset of technologies or varieties from the
mother trial. Each baby trial site is a replicate (Snapp, 2002)
2
The main objective of INNOBAP was to establish a regional multi-stakeholder platform for participatory varietal selection
and innovative post-harvest processing, driven by actors in the value chain (including researchers, growers, extension
services, NGOs, nurserymen, processors, restaurateurs, buyers, sellers, etc.. Such platforms were set up in Cameroon,
Gabon, Guinea and Benin (Tomekpe et al., 2011).
37
Table 7: Overview of technology transfer projects1: multiplication techniques &
awareness creation of the benefits of improved (genetic or sanitary) planting material
Country
Project name
Description of project
Impact statistics
Study
Rwanda
CIALCA-led
macropropagation
activities
Training in
macropropagation and
backstopping of
research and extension
partners
80 trainers (60% from
NGOs), 6 farmers
cooperatives using
macropropagation, 11
coops had expressed
interest. Governments
and private producers
have also expressed
interest
Ouma et al., 2011
PPDR (Centre and
South Provinces)
Training in
macropropagation of
farmer-experimenters,
production of plantlets
1100 farmers trained in
macropropagation
Tomekpe et al., 2011
Cameroon
Macropropagation
training (also in
Ghana, Tanzania,
Mozambique,
Nigeria)
Training of
stakeholders in rapid
multiplication,
information on hybrids,
crop management
practices, pest and
disease management
methods, post-harvest
processing options
An estimated 50 000
people reached through
training and dramatic
increases in planting
material availability
Tenkouano et al.,
2006 ;
Cameroon
IPM technologies for
plantain
Use of improved
plantain management
(including hot-water
and later boiling-water
treatment of suckers)
40% of participants of
training workshops
established demo-plots,
20% of these continued
to plant fields (up to
1ha); sales of increased
bunch weight and more
suckers produced
boosted household
income. 50% of farmers
involved in demo-plots
substituted small fields
for large (<3,5ha) monocropped plots
Tenkouano et al.,
2006 ; Hauser,
personal
communication
Burundi
DR Congo
Cameroon
Lefranc et al., 2010
Questionable how many
farmers continue to use
the technology in
absence of project
(Hauser pers. comm.)
Cameroon
Cameroon
Cameroon,
Gabon
Guinea
Benin.
1
PRFP
TARGET
INNOBAP
Dissemination of
macropropagated
plantlets through formal
partnership with NGOs,
agricultural projects,
producers’
organisations and
extension services
Follow-up training for
100 larger nurseries
(producing 27000
plantlets for 20-30 ha)
Tomekpe et al., 2011
Use of improved
planting materials;
general training on
processing and
marketing
4 hybrids disseminated
to 500 farmers as TC
plantlets
Tomekpe et al., 2011
to establish a regional
multi-stakeholder
platform for
participatory varietal
selection post-harvest
processing
Establishment of multistakeholder
participatory platforms.
Common reference
plots consisting of 10
varieties; a network of
20 individual evaluation
plots
Tomekpe et al., 2011
Lefranc et al., 2010
10 million plantlets
(2004-2006)
300 nurseries
Lefranc et al., 2010
This list is non-exhaustive
38
Table 7 continued
Country
Project name
Description of project
Impact statistics
Study
DR Congo
PARSAR
Training of researchers
and extension officers
in macropropagation.
Thousands of plantlets
distributed and
hundreds of people
trained
Tomekpe et al., 2011
PRESAR
Ghana
TARGET
Technology
advancedment for rural
growth and economic
transformation
4 plantain hybrids,
distributed to 500
producers/year from
2002-05
Tomekpe et al., 2011
Ghana
Peri-urban project
funded by French
Ministry of Food and
Agriculture
Production of banana
and plantain in periurban settings
Researchers and
technicians of crop
research institute
(Ghana) trained by
CARBAP
Tomekpe et al., 2011
2002-05
Ghana
Gatsby
Establishment of a
delivery system for
healthy improved Musa
germplasm with field
tolerance to BSV
2 million plantlets to
4000 smallholders
Tomekpe et al., 2011
Ghana
Developing alternate
food crops
Coconut intercropping
systems for coastal belt
of Ghana
300 smallholders
trained
Tomekpe et al., 2011
Ivory coast
Transfer of
technology to CNRA
Training in
macropropagation and
sensitizing agricultural
entrepreneurs and
producers
Commercial nursery
development, and cooperative of nurserymen
employing 45 workers,
production capacity of
1,5-2 million
plantlets/year
Tomekpe et al., 2011
Transfer of
macropropagation
technology to IITA
technicians and
farmers’ groups
Hundreds of producers
trained, used to produce
local cultivars and
hybrids; emergence of
several nurseries
Tomekpe et al., 2011
Nigeria
Tanzania
Kagera Community
Development
Programme
Improved cultivars and
hybrids tested
25 elite cultivars and
hybrids tested onstation and on-farm;
over one million suckers
diffused via the project
and among farmers
Kikulwe et al. (IFPRI
Improved banana
cultivars and
management
practices)
Kenya
Involvement of
ISAAA, KARI &
JKUAT, Africa
Harvest from the late
90s - 2003
Production and
dissemination of TC
plantlets for farmers
<10% of banana
farmers have adopted
TC
Kabunga et al., 2011a
Uganda
Involvement of the
Ugandan National
extension service
and NARO
Production and
dissemination of TC
plantlets for farmers
Adoption level remains
low. Large regional
fluctuation observed in
profitability of tissueculture, with increased
profitability where
production constraints
and prices are highest
Jagwe et al., 2013
(submitted)
SE Asia &
Pacific
National Repository,
Multiplication and
Dissemination
Centers (NRMDCs)
To enhance the
distribution and
adoption of improved
varieties and TC within
Asia and the Pacific
23 accessions
maintained in NMRDCs
throughout Asia and the
Pacific; including Foc
resistant somaclones
from Taiwan, evaluated
and adopted by
countries experiencing
Tropical Race 4.
NRMDC was used to
initiate adoption of
tissue culture. A
delivery system was
developed to provide
affordable and
accessible seedlings to
small-scale farmers
Molina, 2004 and
personal
communication
39
Table 7 continued
IX.
1
Country
Project name
Description of project
Impact statistics
Study
Oman
University of London,
Ministry of
Agriculture and
Fisheries
Set-up of a tissueculture laboratory to
promote the use of TC
by farmers and boost
national banana
production
Initiated to answer the
need for large
quantities of superior
TC planting materials
following Hurricane
Larry
Training in phenology
of the crop and pests +
on-farm testing of clean
planting material to
reduce nematodes and
weevils; green manure
for weed and fertility
management, methods
for measuring weevil
populations and the
fungus Beauveria
bassiana, for weevil
control.
This project was
initiated in 1995. Oman
currently importas TC
plantlets from Jain Ltd
(India)
Viswanath et al., 2000
TC industry existed for
many years, but
demand only became
important after hirricane
Larry (2005-06)
Singh et al., 2011
60 farmers involved
Williamson et al. 2000
(in Holderness)
Australia
Quality Banana
Approved Nursery
(QBAN) scheme
Latin
America
CATIE IPM
programme in
Nicaragua
Jain, 2013
Gaps in the literature
Several knowledge gaps were identified:
1. There is little quantitative information available concerning the biological
mechanisms and parameters associated with re-infestation of clean planting
materials – from resident infection sources (e.g. where the fallow period was
not long enough to allow population densities to fall below the economic
threshold level), from neighboring fields, via wind dispersal, run-off or
through active infection via virus vectors or migration of pests – nor is there
much information available on the latency periods for Musa pests and
diseases. Re-infestation jeopardizes any benefits associated with the use of
clean planting materials. More information would help to determine
delimitation requirements of quarantine zones, as well as providing useful
information for farmers planning a new field or plantation expansion. One
such study from citrus research, for example, examines a barrier method
used in orchards to reduce the spread of Radopholus citrophilus1 from
infected to non-infected seedlings. Radopholus citrophilus was found to be
unable to migrate in root-free soil. When host roots were permitted to grow
towards one another, conversely, the nematode moved >1.4m in one year
from infected to uninfected seedlings. By pruning the roots of host plants,
they were able to greatly restrict inter-orchard spread of the nematode
(Duncan et al., 1990). Thus, it appears that it may be possible to delimit, to
some extent, the area of infestation within a field. Defining the appropriate
level of protection required and identification of the precautionary measures
to apply has frequently led to much debate.
2. A better understanding of damage caused by pathogen-synergy is required.
A plant is seldom infected by only one pathogen (pest or disease) and there
is little information available on multi-pathogen infections.
3. Experimental data is needed to quantify the relationship between sanitary
quality and multiplication method. Likewise, the potential yield associated
with tolerance levels should be determined for buyers (and sellers) to
evaluate the relative importance of non-compliance with quality standards for
planting materials.
Radopholus citrophilus Huettel, Dickson and Kaplan, 1984 syn. R. similis, citrus race (Loof, 1991)
40
4.
5.
6.
X.
Considering the BSV activation risks associated with tissue-culture
propagation of AAB cultivars, more research is needed in order to define
appropriate protocols for the safe movement of AAB germplasm.
A better understanding of existing and past initiatives is needed – NRMDCs,
tissue-culture in East Africa and follow-up of on-farm trials where paring,
boiling- and hot-water treatment were used. An improved understanding of
adoption constraints and ex post analysis of the socio-economic benefits for
small-scale farmers is advocated. For example, how many of the farmers
that were exposed to improved management for Musa planting materials,
are still using the technology after the subsidies and technical assistance
has been withdrawn? Technologies transferred to small-scale farmers as
management options for Musa pests and diseases are often advocated
based on a low investment cost in monetary terms. Often, however, the
additional labour requirements are not equally considered. Adoption of
innovative technologies carries both an implementation cost and an
opportunity cost, which relates to the alternative uses of resources required
for adoption.
More effort is required to improve robustness of regional strategies. Several
national strategies exist for the provision and/or certification of Musa planting
material, as well as regulations on an international level.
Conclusions and integrated perspectives on challenges and opportunities for
small farmer access to improved Musa planting materials
Numerous methods have been developed to obtain clean planting materials, each
differing in complexity and accessibility for small-scale farmers. For many farmers,
conventional suckers allow the availability of reasonably healthy, viable planting
material of preferred cultivars without undue cost or effort. However, the local system
is not static. New generations establish their own households, land use is intensified,
new crops are introduced and market opportunities arise. Pests and diseases may be
introduced or become more important due to changes in production systems (Staver
et al., 2010).
There is a need to better understand the conditions that stimulate the adoption of
clean planting methods. Whether cost intensive or extensive in terms of financial and
human capital, the current level of adoption of transferred technologies for Mus seed
systems appears to have been marginal at best. The use of cleaning practices that
require the least investment, such as paring and thermotherapy, are still not
widespread despite their simplicity and effectiveness, indicating challenges in the
diffusion of technologies to rural communities. Some countries have been more
successful than others (e.g. Costa Rica and India), highlighting the importance of the
support that can be provided though public policies. Methods producing larger
quantities of clean planting materials, such as micro- or macropropagation, are
frequently hindered by a lack of local capacities, including labor, skills and
infrastructure, as well as weak institutional support.
Various studies have examined the characteristics and challenges associated with
technology transfer to small-scale farmers. Löffler and Louwaars (2007), discuss
distinctive features common to African farming systems, where degraded soils of
poor fertility are often subject to erratic rainfall and endemic plant and animal
diseases further decrease production. Compared to other global regions like Asia,
Africa is characterized by a relatively low population density. Underinvestment in
agricultural R&D and rural institutions and infrastructure is a common feature. Many
parts of Africa lack an effective knowledge infrastructure and efficient academic
institutions. Brain drain prevails over brain gain. Customary land tenure is the
predominant relationship between people and the land.
41
Many of the characteristics listed by Löffler and Louwaars (2007) can be applied to
Musa production systems around the world. Musa production methods are extremely
heterogeneous and subject to a low R&D investment compared to other staple crops
of comparable global significance for food security1. For example, out of the nearly
130 countries worldwide that produce Musa, only 6 have public breeding programs
(Lescot, 2012).
The success of the Green Revolution in Asia and Central America stimulates some to
call for an African Green Revolution. However, due to the complexity of the African
situation, and the diversity of African regions, The InterAcademy Panel (2004) in their
study ‘Realizing the promise and potential of African agriculture’ calls for a ‘Rainbow
Evolution’ instead. The Rainbow-element designates the necessity of a number of
concerted actions that may differ in various regions: the Evolution-element refers to
the fact that no change can be implemented without using the current agricultural
practice in the different farming systems as a starting point (Löffler and Louwaars,
2007). Likewise, Staver et al. (2010) emphasize that to improve the Musa seed
system, the challenge for breeders, agronomists and rural development planners, is
not to convert all farmers to commercial seed use, but to target actions and zones
where improved seed quality may have the highest impact.
In a priority setting exercise to characterize national Musa seed systems using
selected key criteria, Staver et al. (2010) ranked various limiting factors, obstacles
and opportunities inherent to national seed systems. On the demand side, three main
challenges were recognized: the genetic diversity and sanitary quality of Musa
planting materials and, the need for a sufficiently large commercially oriented farming
sector in order to sustain market demand. From the supply side, a major constraint
was in-country capacity to implement strategies to improve the quality of farmer
planting material (Staver et al., 2010).
The implementation of training programs for national quarantine services were
identified as an important strategy in the improvement of national Musa seed
systems. For countries where BBTV is present, within-country quarantine measures
are also advocated. At present, quarantine services in many Musa producing
countries lack awareness of the threat and primary risks associated with introduction
of such diseases as Foc race 4 and BBTV; while countries where BBTV is already
present often lack detection capacity and infrastructure to conserve virus-free
germplasm (Staver et al., 2010).
Suggested interventions:

Quarantine officers from countries lacking experience may benefit from
training provided by quarantine officers from more experienced countries.

A needs assessment should be carried out to evaluate availability and quality
of online infrastructures that may assist quarantine facilities in developing
countries (e.g. coupling CABI Crop Protection Compendium to proMusa
specialist services?).

Development of regional online hubs of information relevant to Musa
quarantine services could provide additional support with minimal
investment.
In many Musa producing countries a more accessible and reliable information
network would benefit both the capacity of national quarantine services, especially
remotely stationed duty posts, or help to develop a market for traditional or improved
planting materials. Numerous reports can be found of mobile phone initiatives tailored
to the needs of farming households (UNCTAD, 2010). Mobile phones could similarly
empower national (especially remotely stationed) quarantine services. Mobile phones
are relatively inexpensive, require no special training, serve social functions and help
1
Total global production ranks fourth after maize, rice and wheat (faostat.fao.org).
42
reduce the information gap between farmers and traders (Deichmann and Wood,
2001). In developing countries, the subscription rate is now 58 per 100 people, and
rising rapidly, with the rate in the poorest Least Developed Countries (LDCs) up at 25
from only 2 per 100 a few years ago (UNCTAD, 2010). In India, mobile phone
coverage has seen exponential growth, helping small farmers to overcome
informational asymmetries that limit their bargaining power in traditional supply
chains (Dev, 2012). In 2003 Kenya's Agricultural Commodities Exchange and mobile
operator Safaricom launched a text-messaging platform (SokoniSMS64) to provide
pricing information to farmers. M-Farm offers a similar service, while the iCow is a
mobile app billed as "the world's first mobile phone cow calendar" – an SMS and
voice service that allows dairy farmers to track their cows gestation, acting in effect
as a veterinary midwife. Farmers are also given tips via iCow on breeding and
nutrition (Ogunlesi and Bursari, 2012).
Suggested interventions:

Exploitation of mobile phone networks and rural radio services in resource
poor settings may assist fast and reliable information transfer for isolated
locations. Locating buyers and sellers of Musa planting materials may thus
be facilitated using mobile phone technology.

Mobile phones may also be used to provide quality certificates for in-country
or regional germplasm transfer. For example, local phytosanitary officers
could give temporary codes to farmers or traders of planting materials, after
positive inspection of the batch of suckers of plantlets. Upon sending this
code to a central quarantine service, the farmer may receive a text message,
detailing quantity and quality, source and destination. This would allow
national services to quickly map national and regional germplasm transfer
networks and allow better-targeted future interventions.
The diversity of Musa genetic quality demands a two-fold approach when considering
national seed systems in order to meet the demand for improved quality of the most
preferred cultivars, while conserving the diversity as agreed among signatories of
international treaties on biodiversity and plant genetic resources. Depending on the
number of types and cultivars present, the national seed system will face a relatively
simple or vastly more complex task in responding to demand (Staver et al., 2010).
Suggested interventions:

The establishment of certified mother plant gardens to preserve local genetic
resources and serve as a source of virus-free and true-to-type mother plants
is advocated. Where local diversity is less pronounced, importation of
additional cultivars might be warranted as a source of resistance to pests and
diseases.

Virus testing at such conservation gardens may be coupled to give support to
local quarantine services.

Care should be taken to locate such gardens in localities representative of
the most frequently occurring soil and climatic conditions.

Where resources are restricted, regional gardens may be more feasible,
under the condition that regional germplasm transfer regulations are
harmonized.
Presence of BBTV was used as a key criterion for the promotion (or not) of tissueculture. Where BBTV had not (yet) been identified in a country, macropropagation
was advocated (Staver et al., 2010). A more pragmatic approach currently in its test
phase, promotes the use of ELISA testing in combination with macropropagation in
countries with minimal tissue-culture production capacity. Pilot trials are being
evaluated in DR Congo (Mobambo and Vangu, 2012).
43
The study by Bortagaray and Gatchair (2012) highlights the multifaceted nature of
frameworks that enable (or hinder) Musa seed system interventions. Studying the
distributive dynamics of tissue-culture banana production, access and use in Costa
Rica and Jamaica they identified a range of interlinked factors, including: general
educational levels, technical competence, and institutions (commercial, industrial,
financial), as well as other factors such as economies of scale and trade effects.
It is impossible to identify a one-size-fits-all approach to address the challenges
pertaining to the improvement of Musa seed systems. A comparison of the success
of interventions to stimulate the use of tissue-culture or macropropagated plantlets,
shows easier adoption by medium- and large-scale market-oriented farmers in
demand driven scenarios. Examples of demand-driven technology adoption include
biofabricas in Latin America, which are semi-industrial scale propagation centers
producing tissue-culture plantlets of various crops and, tissue-culture production
industries in India, China and South Africa. Small-scale farmers, by contrast, have
generally been exposed to multiplication technologies in a supply-driven scenario.
Main examples are the NGO- and government-sponsored donations and subsidies in
West and Central Africa, the donations or micro-credit mediated technology transfer
in East Africa and the NRMDCs in Asia and the Pacific. Many of these field trials and
dissemination exercises would benefit from a rigorous ex post analysis of socioeconomic benefits and evaluation of the success rate of adoption, i.e. how
sustainable and far-reaching has the technology been in the long run, before
investing in new large scale dissemination efforts. There is, for instance, little
documented evidence in the literature of long-term adoption of many of these
technologies by small-scale farmers.
44
XI.
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