PROJECT
OBJECTIVES
PROGRESS AND HIGHLIGHTS
 It has been shown through Koch’s postulates that elephant hide on potato
in South Africa is caused by Rhizoctonia solani A3
 The predominant AG group is AG3, with AG2.1, 2.2, 4 and 5 and binucleates also occurring
 This was the final year of the project
Characterisation and symptomology of
Rhizoctonia solani
 Characterisation of Rhizoctonia isolates that are pathogenic
on potatoes in South Africa
 To determine whether Rhizoctonia causes symptoms
elephant hide
Conservation tillage in the Sandveld
 Development of guidelines for conservation tillage practices
in the Sandveld
 Evaluation of conservation tillage on yield, physical chemical
and biological status of soil
 Evaluation of the effect of conservation tillage on water use
efficiency
 To determine the effect of conservation tillage on soil
microbe populations and prevalence of soil-borne diseases
 The trial site for this long-term project was established and soil
characteristics established viz soil physical characteristics, CO2-biological
activity, nematode population and microbe population
 Soil was prepared using three tillage methods before potatoes were
planted.
 Three cover crops have been sowed when potatoes were harvested
Control of post-harvest diseases
 To test the effectiveness of different sanitizers used to
reduce post-harvest rotting of potatoes
 To conduct trials on farms in different regions
 Five sanitizers with different active ingredients were tested and found to
differ in their ability to control soft rot after harvest
 An on-farm trial showed that sanitizers alone cannot control post-harvest
rotting. Factors such as harvest method, ambient temperature and general
sanitation in the pack house can also play a role
Development of an integrated
management plan to control common
scab (Streptomyces species)
Development of an integrated
management plan for the control of
powdery scab (Spongospora
subterrainea f.sp. subterrainea)
Characterisation and monitoring of
virus and virus races in South Africa
Investigation into the possible effects
of climate change on potato
production
 To determine the role of soil inoculum, soil characteristics,
rotation crops and microbial activity on the incidence of
common scab in three localities
 To develop a management strategy for each locality based
on the results obtained for each locality
 To determine susceptibility of commercial cultivars to
Spongospora subterrainea f.sp. subterrainea
 To test the effect of fumigants, soil conditioners and
biological control agents
 To develop a user friendly test to determine whether soil is
infected with the pathogen
 Sequencing of the whole genomes of 20 South African
isolates of PLRV from the all potato growing areas in South
Africa in order to assess the difference between nonpathogenic European strains of PLRV and SA strains of PLRV.
 To monitor the spread of PLRV isolates during a growing
season
 To determine the possible effects of climate change on yield
in three production regions (Sandveld, Eastern Free State
and Limpopo)
 Analysis of more samples of fissure scab confirmed that Streptomyces
species is the cause of the diseases. It appears also that fungal species, and
other factors may also be involved
 Trials to test the effect of cover and brassica crops are on schedule
 The second year’s trials confirmed that currently no cultivar has resistance
against powdery scab. Some cultivars showed more tolerance, however.
 The past years results showed that in order to evaluate cultivar resistance,
galls formation on roots, as well as pustules on tubers must be rated
because root galls can contribute to inoculum build-up in the soil
 PLRV isolates are more closely related to isolates from the USA and
Australia than to European isolates.
 Virus tests showed that Polymerase Chain Reaction (PCR) techniques is
more sensitive than the Elisa technique
 The Elisa technique effectively detect the new strains of PVY (PVYNTN and
PVYWILGA)
 Growth model simulations indicate that between 1960 and 2050, the
average temperature will rise by 1.9 oC and the CO2 concentration will
increase from 315 to 550ppm. In general potato yield can be expected to
 To determine the possible effects of climate change on the
incidence of potato pests and diseases in the mentioned
production regions
Potatoes South Africa aphid
monitoring network
 To provide seed growers to the commencement of aphid
flights in order to reduce the risk of virus
Effect of climate on the activity and
intensity of virus vectors in the winter
rainfall region
 To monitor plant aphid numbers to determine how climate
affects the activity and intensity of plant virus vectors
Future management of the risk of root
knot nematode
 Establishment of PCR identification techniques and
identification of root-knot nematodes from different regions
Promotion of good irrigation
scheduling practices
Soil water monitoring in the Sandveld
Survey of the status of arthropod pests
on potatoes at regional and national
level
 Evaluation of different irrigation scheduling products on a
number of farms in the Sandveld and Limpopo production
regions
 To promote irrigation scheduling to improve water use
efficiency and reduce electricity cost
 To determine the impact of the water use for potato
production on soil water levels in the Sandveld
 To carry out a survey in each production region to determine
the status of potato pests in order to develop a map on the
distribution of pests in South Africa
 The objective for the current year were to carry out surveys
in Kwazulu-Natal and North Eastern Cape
increase. However, hot regions will benefit the least.
 In Limpopo more frost free days can be expected, thus reducing the risk
during winter production. But yield of late- and early summer plantings will
decrease as a result of the higher temperature.
 Incidence of soft rot, black leg, root-knot nematode and aphids is likely to
increase. Early blight and brown spot is likely to increase during wet
Sandveld winters and eastern Free State summers. Late blight incidence is
expected to decrease in all regions except the wet Sandveld winters
 The centralised internet based database has been updated to provide
vector pressure indices from aphid data from suction traps. Vector
pressure indices is a more accurate measure of virus risk than aphid
number as aphid species differ in their ability to transmit virus.
 The relationship between plant aphid numbers and rainfall has been
confirmed during the past season and that planting after April poses the
least risk for virus infection in the Sandveld
 Meloidogyne enterolob, reported for the first time on potato in South
Africa, is generally described as a species from tropical regions. The species
was, however, identified in tubers from cooler production regions in South
Africa
 This was the final year of the project
 The hardware, recommendations and services of two commercial
products were tested on four farms in Limpopo
 Commercial irrigation scheduling products were tested on six farms in the
Sandveld
 Some produces comments were that assistance needed with probe
installation, setting up of management lines, data interpretation, less was
irrigated, but yields still excellent
 Observations of the last year indicate that of 26 boreholes monitored for
ground water levels, the level has risen in eight and in 18 the level has
dropped.
 In the 52 bore holes monitored for water quality, the EC has improved in
23 and has decreased in 29
 Long term observations are starting to show trends and wil be continued
 In Kwazulu-Natal and North Eastern Cape, the most common pests are
aphids, the potato tuber moth and leaf miners
 In Kwazulu-Natal, pests of secondary importance are: potato snout beetle,
nematodes and white grubs
 In the North Eastern Cape the pests of secondary importance are: cut
worms, nematodes and caterpillars
 Black farmers identified millipedes as a problem
 All farmers apply insecticides successfully to protect their crops.
In vitro maintenance of open potato
cultivars
Effect of calcium fertilisation on potato
production in South Africa
Early cultivar evaluation in South Africa
 Maintenance of open – and licenced ARC cultivars in vitro
 To make nuclear material available for mass production by
commercial tissue culture laboratories
 To determine the effect of calcium in irrigation water on the
yield and quality of potatoes
 To comprehensively evaluate pre-commercial cultivars in
four different climate regions in South Africa
 Thus the results of this project contributes towards
identification of high-yielding and widely adapted cultivars
 To contribute to speedy commercialisation of new cultivars
 In vitro plants were delivered to five commercial laboratories
 Infrastructure and methodology for studies on different soil types have
been established
 Evaluation of 12 cultivars was done on four farms viz Dendron (Limpopo),
Tala Valley (Kwazulu-Natal), Aurora (Sandveld) and Petrus Steyn (Eastern
Free State)
 The production methods, climate and prevalence of pests and diseases in
the four areas differed considerably. The value of cultivars for specific uses
could thus be identified.
 One new cultivar for the fresh market, one dual purpose cultivar were
identified and one for processing