ACTA AGRICULTURAE SCANDINAVICA, SECTION B — SOIL & PLANT SCIENCE
2020, VOL. 70, NO. 2, 95–108
https://doi.org/10.1080/09064710.2019.1674915
Combining ability of yield and yield components among Fusarium oxysporum f.sp.
strigae-compatible and Striga-resistant sorghum genotypes
Emmanuel Mremaa,b, Hussein Shimelisa and Mark Lainga
a
School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Scottsville, Pietermaritzburg, South Africa; bTanzania
Agricultural Research Institute Tumbi Center, Tabora, Tanzania
ABSTRACT
Use of sorghum [Sorghum bicolor (L.) Moench] cultivars with partial resistance to Striga spp. and
Fusarium oxysporum f.sp. strigae (FOS) represents a novel strategy to control Striga. This study
aimed to identify the nature of gene action controlling grain yield and yield components and to
select promising sorghum crosses possessing both FOS compatibility and Striga resistance, along
with good combining ability effects. One-hundred hybrids, developed from pairwise matings
among 10 FOS compatible, high-yielding female lines and 10 Striga-resistant male lines, were
evaluated with and without FOS inoculation. The F1s were field evaluated at three locations in
Tanzania known for their severe Striga infestation, using an alpha lattice design with two
replications. General (GCA) and specific combining ability (SCA) variances were significant for
grain yield per plant, hundred-seed weight, plant height, flowering time and the number of
Striga plants. The study demonstrated FOS inoculation to be an effective means of controlling
Striga. Families 675 × 672, AS435 × 3993 and 4643 × AS436 displaying large SCA effects for grain
yield, and 4567 × AS429, 3424 × AS430 and 3424 × AS436 with small SCA effects for Striga counts
should be useful genetic resources for breeding and integrated Striga management.
Introduction
Striga infestation is one of the main constraints to
sorghum production in sub-Saharan Africa (Watson
et al. 2007). Striga hermonthica [Del.] Benth and Striga
asiatica [L.] Kuntze are the two main obligate parasitic
weeds that inflict severe yield losses, reaching up to
100% in susceptible sorghum cultivars (Riches 2003).
However, the level of yield loss depends on the extent
of infestation, climatic conditions and control measures
used. Both S. hermonthica and S. asiatica parasitize
several cereal crops, including maize (Zea mays L.),
sorghum, millet (Pennisetum glaucum L.) and upland
rice (Oryza sativa L.) across extensive agro-ecological
areas in African countries, including Tanzania. Poor soil
fertility, use of a single method of Striga management
and cereal mono-cropping are among the major causes
of Striga perpetuation and high yield losses in sorghum
(Parker 1991). Each Striga plant can produce 5000–
84,000 seeds that remain viable in the soil for up to 20
years (van Mourik et al. 2008).
S. hermonthica and S. asiatica infestation have
reached epidemic proportions in the semi-arid areas of
the Lake, Western and Central Zones of Tanzania,
where the parasite is a serious threat to sorghum
ARTICLE HISTORY
Received 14 August 2019
Accepted 25 September 2019
KEYWORDS
Biological Striga control;
combining ability; Fusarium
oxysporum f.sp. strigae;
resistance breeding; sorghum
production. In these areas, farmers are often compelled
to abandon their farmlands because of Striga infestation,
and switch to cultivation of non-host crops. In some
localities, farmers grow unimproved sorghum landraces
that are less susceptible to Striga (Mrema et al. 2017a).
The use of resistant cultivars, biological agents, cultural practices and chemical control methods are important strategies to manage Striga infestation (Kenga et al.
2004). These strategies promote sorghum growth and
development and reduce germination and development
of juvenile Striga plants (Kenga et al. 2004). The combined use of various Striga-management options and
understanding the biological and metabolic relationships between the host and parasite are important prerequisites for the implementation of integrated Striga
management (ISM) (Reda and Verkleij 2004). The use of
resistant cultivars is the most environment-friendly and
economical Striga-management option for millions of
smallholder farmers in sub-Saharan Africa, who depend
on sorghum production for their livelihoods. The use of
sole host resistance was however not effectively in
areas with high Striga infestation. In Tanzania for
example, the use of partially resistant sorghum lines,
Wahi and Hakika, has not been effective in areas with
CONTACT Emmanuel Mrema
mremaemmanuel@yahoo.com
School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, P/
Bag X01, Scottsville, Scottsville, Pietermaritzburg 3209, South Africa; Tanzania Agricultural Research Institute Tumbi Center, P.O. Box 306, Tabora, Tanzania
© 2019 Informa UK Limited, trading as Taylor & Francis Group
96
E. MREMA ET AL.
high levels of Striga infestation. These lines were also
reported to be low yielding, while the high-yielding varieties Pato and Tegemeo are susceptible to Striga
(Hearne 2009). Introduced varieties, such as Macia and
Serena, have not been adopted mostly because they
are susceptible to Striga, birds, storage pests and harsh
environmental conditions, such as low rainfall and poor
soil fertility. Low levels of adoption of introduced cultivars that lack some farmers’ preferred traits have been
reported in Ethiopia. To facilitate adoption of new
sorghum varieties, it is important to consider farmers’
preferred traits like resistance to Striga infestations, earliness, drought tolerance, grain yield, resistance to pests
and diseases as well as resistance to bird attacks
during the breeding stages (Mrema et al. 2017a).
There are many arbuscular mycorrhizal strains (Fusarium oxysporum f. sp. Lini and F. oxysporum f. sp. Strigae)
have been suggested for biological control of pathogens
in plants. They compete with plant pathogens or parasites for nutrients and space, by producing antibiotics,
parasitizing pathogens, or inducing resistance in the
host plants (Berg et al. 2007). Furthermore, they cause
biochemical changes in plant tissues, microbial
changes in the rhizosphere, nutrient status, anatomical
changes to cells, changes to root system morphology
and stress alleviation (Berg et al. 2007). Biological
control involves the use of microbes to control Striga
and can be applied to smallholder farming systems
(Rebeka et al. 2013). Like resistant cultivars, the ‘biological methods’ is also affordable and environment-friendly
(Abbasher et al. 1998).
Pathogenic isolates of F. oxysporum f.sp. strigae (hereafter referred to as FOS) are reported to be effective bioherbicides for managing Striga infestation in sorghum,
particularly when the method is integrated with host
resistance and fertilizer application (Ayongwa et al.
2011; Rebeka et al. 2013). The fungus destroys Striga
before the weed penetrates the roots of sorghum
(Rebeka et al. 2013). The FOS is reported to be hostspecific, its inoculum can be mass-produced easily
(Ciotola et al. 2000). When sorghum seeds are treated
with FOS, the fungus colonize in the rhizosphere of the
sorghum plants. It infects and inhibits growth and development of Striga, stopping it from parasitizing the roots
of the host plant.
One of the main goals of sorghum breeding programs
is to develop sorghum genotypes that are resistant or
tolerant to Striga and possess farmer-preferred traits
and compatibility to FOS (Shayanowako et al. 2017). To
be able to devise an effective selection procedure for
resistance to Striga, knowledge of genetic control and
inheritance of sorghum traits of sorghum is essential.
The FOS compatibility of a genotype is discerned by
the magnitude of differential responses between the
FOS-treated and untreated genotypes grown under
similar Striga-infested conditions. Crosses between
parents from genetically unrelated populations or
different heterotic groups may yield suitable genetic
recombinants and superior transgressive segregants
(Makanda et al. 2009; Konate et al. 2017). Thus, the
knowledge of the nature of gene action controlling
quantitative and qualitative traits of economic importance and FOS compatibility of genotypes is desirable.
Both the general combining ability (GCA) effects of
parents and specific combining ability (SCA) effects of
their crosses are important in conditioning economic
traits (Stoskopf 1993). General combining ability represents mainly the additive and additive × additive
types of genetic variance, whereas SCA is mainly attributable to genes with dominance and/or epistatic effects.
Combining ability tests based on mating designs, such
as North Carolina Design II (NCD II) and diallels, are
useful in selecting suitable parents and transgressive
segregants from given crosses to use in breeding programs and to determine the subsequent selection procedure to use.
In an attempt to select Striga-resistant and FOS-compatible sorghum lines, promising genotypes were identified through controlled evaluations, as reported by
Mrema et al. (2017b). Some of the selected landraces
were poor yielders but adapted to the drier regions of
Tanzania and possessed farmer-preferred traits (Mrema
et al. 2017b). In contrast, some of the introduced
sorghum genotypes had better yield potential and FOS
compatibility, but they lacked farmer-preferred traits.
Mutengwa et al. (1999) and Haussmann et al. (2000)
employed several genetic parameters to investigate the
gene action controlling Striga resistance in sorghum.
They reported on the influence of a single recessive
gene in controlling low germination stimulus in
sorghum cultivars. However, there is still a need to elucidate the genetic effect of Striga resistance in sorghum
when integrating FOS as a biological control of the parasite. Understanding of this effect among the developed
sorghum families could fill the current knowledge gap
relative to the best breeding methodology to adopt in
advancing both Striga resistant and FOS-compatible
families. Therefore, the objective of this study was to
identify the nature of gene action controlling grain
yield and yield components and to select promising
sorghum crosses possessing both FOS compatibility
and Striga resistance, along with high combining ability
effects. We tested the hypothesis that additive genetic
effects could be important in controlling Striga resistance
and that the new families possessing farmer-preferred
traits could be selected.
ACTA AGRICULTURAE SCANDINAVICA, SECTION B — SOIL & PLANT SCIENCE
Materials and methods
Plant materials and crosses
One-hundred single-cross hybrids developed using 10
females and 10 male sorghum lines and 2 checks were
evaluated in the present study. Crosses were made
using the North Carolina Design II. Information regarding
the 20 parental lines used to generate the crosses is
given in Table 1. The genotypes used were identified in
a previous study (Mrema et al. 2017b). These materials
had varied levels of reaction to both S. hermonthica
and S. asiatica. Resistant lines are those that exhibited
less Striga counts than susceptible ones. FOS-compatible
lines manifest FOS proliferation and reduced Striga count
under FOS treatment (Mrema et al. 2017b). Further, the
selected lines had most of the farmer-preferred traits in
the semi-arid areas of Tanzania (Mrema et al. 2017a).
Bio-control agent and inoculation preparation
A pathogenic strain of the bio-control agent,
F. oxysporum f.sp. strigae (FOS), obtained from northeastern lowlands of Ethiopia was used in this study
(Rebeka et al. 2013). The strain was positively diagnosed
at Humboldt University’s Phytomedicine Division and its
isolates were maintained at −40°C on special nutrient
agar (SNA) medium (Rebeka et al. 2013). Previous
reports confirmed the pathogenicity and host specificity
of the FOS isolate to Striga (Rebeka et al. 2013; Mrema
et al. 2017b). Cultures were grown on potato dextrose
agar (PDA) and pure chlamydospores were extracted
and mass produced at Plant Health Products Pvt Ltd.,
Kwazulu-Natal, South Africa and stored at the University
97
of KwaZulu-Natal’s Plant Pathology Division. About 500
seeds of each sorghum genotype were surface sterilized
using 70% ethanol and soaked in 1% sodium hypochlorite solution, in 2 different steps, for 30 min for both the
FOS-treated and untreated seeds. The seeds were dried
under a laminar airflow hood and coated with FOS
using the procedure described by Elzein et al. (2006),
which involved film coating of each seed with a
mixture of 40% Arabic gum and fresh spores of FOS
and drying under a laminar airflow hood.
Experimental locations
One-hundred sorghum hybrids and two standard check
cultivars (‘Macia’, widely grown in Tanzania and ‘AS436’
introduced from ICRISAT-India were included as susceptible and resistant checks, respectively) were evaluated
at three locations, viz., Igunga, Misungwi and Kishapu
from Tabora, Mwanza and Shinyanga regions, respectively (Table 2). Igunga district is found in the western
part of Tanzania. During the growing season, the area
received a unimodal rainfall, with a mean of 134 mm. It
has a long dry season of about 5–6 months and temperatures ranging from 17.50°C to 29°C. The site is characterized by sandy to loamy soils. The Kishapu and Misungwi
districts are in the lake zone. The areas are characterized
by the presence of undulating plains with rocky hills and
low scarps. The districts have well-drained soils with low
fertility and a growing season running from December to
March. The two sites experience temperatures ranging
from a mean of 19–28°C. Field evaluations were conducted during the main cropping season of December
2015 to April 2016 with and without FOS application.
Table 1. List and descriptions of parental sorghum genotypes used in crosses.
Entrya
Name
Sourceb
1
4567
Magu/Tanzania
2
675
Attributes
High yielding, medium maturing and
FOS compatible
Early maturing and FOS compatible
Entrya
Name
Sourceb
11
AS436
ICRISAT/India
Attributes
Early maturing, medium yielding and
Striga resistant
Medium maturing and yielding, and
Striga tolerant
Medium maturing and Striga resistant
Tarime/
12
AS426 ACCI/South Africa
Tanzania
3
1563 Bukoba/
FOS compatible, early maturing and
13
672 Musoma Rural/
Tanzania
high yielding
Tanzania
4
AS435 ACCI/South
High yielding and late maturing
14
3993 Serengeti/Tanzania Early maturing and Striga tolerant
Africa
5
4643 Misungwi/
FOS compatible and early maturing
15
AS430 ACCI/South Africa
Early maturing and Striga tolerant
Tanzania
6
104 Kishapu/
Striga susceptible, early maturing and
16
AS429 ACCI
Early maturing, Striga resistant and
Tanzania
high yielding
medium yielding
7
4031 Ukerewe/
Early maturing and high yielding
17
3937 Serengeti/Tanzania Striga resistant and medium maturing
Tanzania
8
3424 Igunga/
FOS compatible and medium maturity
18
630 Serengeti/Tanzania Striga resistant and medium maturing
Tanzania
9
AS422 ACCI/South
High yielding and early maturing
19
654 Bunda/Tanzania
Striga resistant and medium maturing
Africa
10
3984 Musoma/
FOS compatible, high yielding and late
20
AS424 SARC/Ethiopia
Early maturing and Striga tolerant
Tanzania
maturing
a
Entries 1–10 were used as female parents and 11–20 as male parents.
b
ACCI, African Centre for Crop Improvement; ICRISAT, International Crops Research Institute for the Semi-arid Tropics/India; and SARC, Sirinka Agricultural
Research Centre in Ethiopia.
98
E. MREMA ET AL.
Table 2. Descriptions of the three locations used for evaluation of crosses and standard checks.
Location
Region
Mbutu
Tabora
Mwanangwa
Mwanza
Isoso
Shinyanga
a
Min: minimum temperature.
b
Max: maximum temperature.
Latitude (°South)
Longitude (°East)
Altitude (m)
Rainfall (mm)
Temp (Mina, °C)
Temp (Maxb, °C)
4.23
2.96
3.62
33.91
33.16
33.84
1060
1176
1126
134
235
234
17.50
19.33
19.33
29
28
28
The study locations represented the semi-arid areas of
Tanzania and were known for sorghum production and
infestation by both S. hermonthica and S. asiatica.
Experimental design and trial establishment
The crosses were field evaluated using a 10 × 10 alpha
lattice experimental design with two replications at
each location, using three-row plots. Two sets of plots
were used in each treatment; one plot was planted
with sorghum seeds treated with 75 mg of Fusarium
chlamydospores, whereas the other plot was planted
with each genotype without Fusarium treatment. Each
plot was 2.7 m × 2.7 m. Each replication consisted of
the 100 hybrids randomly allocated across 10 incomplete
blocks, each with 10 genotypes. One resistant and one
susceptible checks were included in each replication as
comparative control. The FOS treatments were: (1)
seeds inoculated with FOS and (2) seeds without FOS
inoculation. Before planting, to ensure even distribution
of Striga population, artificial Striga infestation was done
according to Berner et al. (1997); wherein a scoop of 1:99
ratio of Striga seed and sand mixture was used. This
ensured delivery of about 5000 viable Striga seeds per
study site. This was done after preconditioning the
seeds by drenching the mixture in water and incubating
it for a week at room temperature. Sorghum genotypes
were planted using an inter-row spacing of 90 cm and
an intra-row spacing of 30 cm. Two seeds per hill were
sown and, two weeks after planting, plots were
thinned to keep one seedling per hill, which gave a
plant density of 37,037 ha−1. Three weeks after planting,
60 kg ha−1 of NPK (20-10-5) fertilizer was applied. The
crops were raised under rain-fed conditions. Weeds
other than Striga were removed manually immediately
upon emergence. To control stem borer, Attakan
C344SE, a systemic insecticide (C22H19Cl2NO3), was
mixed with water in a ratio of 15 ml of Attakan C344SE
to 20 l of water and foliar-sprayed on the crop at a rate
of 1 l per 50 m2. During seed-set and grain-filling
stages, fungal diseases were controlled through two
scheduled applications of hexaconazole 5 EC, a systemic
fungicide, at a rate of 30 ml per 20 liters of water. Bird
scares were implanted in the middle and corner sections
of each field to prevent possible bird damage.
Data collection and analysis
Data on sorghum and Striga parameters were collected.
Twenty sorghum plants from the middle rows in each
plot were tagged for data collection. The parameters
measured included days to 50% flowering (expressed
in days [d]), plant height (expressed in cm) measured
at 50% flowering, seed yield (g/plant) and weight of
100 seeds (g/100 seed). When sorghum plants attained
50% flowering, a quadrant of 13.77 m2 was placed
around sampled plants and the numbers of Striga
plants in the quadrant were recorded. The data were
analyzed using the procedure for an alpha lattice
design in SAS (SAS 2011). Combined analysis of variance
(ANOVA) across the three sites was performed for the
two FOS treatments, after conducting tests for normality
of the data and homogeneity of variances. Independent
samples t-test was conducted to assess the significant
differences among sorghum genotypes for agronomic
performance and Striga number attributable to FOS
treatments. Genotypes were considered a fixed factor,
whereas locations, replications and incomplete blocks
were treated as random factors. General combining
ability effects of females and males, the SCA effects of
crosses, and their interactions with the locations were
computed according to the NCD II using the following
model:
Yijk = m + gi + gj + Sij + ek + (ge)ik + (ge)jk + (se)ijk
+ eijk,
where Yijk is the performance of the cross between the
ith male and jth female, in the kth location, μ is the
mean; gi is the GCA effect of the ith male parent; gj is
the GCA effect of the jth female parent; Sij is the interaction of the ith male parent with the jth female
parent; ek is the effect of the kth location; (ge)ik is the
interaction of the gi and ek; (ge)jk is the interaction of
the gj and ek; (se)ijk is the interaction between sij and
ek; and ēijk is the residual.
Significance of male × female interaction effects (SCA)
was determined against the residual mean square. The
ratio between the sum of squares of GCA of parents
and SCA of crosses was also calculated according to
Singh and Chaudhary (1979). The GCA effects of
parents were computed as a deviation of the parent
ACTA AGRICULTURAE SCANDINAVICA, SECTION B — SOIL & PLANT SCIENCE
mean from the mean of all hybrids (Singh and Chaudhary
1979). The SCA effects were computed as a deviation of
each cross mean from the mean of all crosses, adjusted
for corresponding GCA effects (Singh and Chaudhary
1979).
Expected mean square (EMS) values for males (EMSm),
females (EMSf) and the interaction between males and
females (EMSfm) were computed using the following
equations:
EMSm = s2e + r s2fm + rf s2m ,
EMSf = s2e + r s2fm + rms2f ,
and
EMSfm = s2e + r s2fm ;
where r is the number of replications; f is the number of
females used and m the number of males used. Assuming the coefficient of inbreeding (F ) = 0, error variance
(σw 2) = total variance (δ 2P) – covariance of full sibs
(CovFS) = ½ δ 2A+ ¾ δ 2D + δ 2EW; female and male variance
σ 2FM = covFS – covariance of half sibs (covHS) = ¼ δ 2D;
male variance σ 2m = female variance σ 2F = Cov(HS) = ¼ δ 2A;
total variance (δ 2P) = σ 2W + σ 2FM + [(σ 2F + σ 2M)/2]; male additive variance (δ 2AM) = 4σ 2M; female additive variance
(δ 2AF) = 4σ 2F; dominance variance (δ 2D) = 4σ 2FM, environmental variance (δ 2EW) = σ 2w – (½δ 2A + ¾ δ 2D); heritability
h 2 = 2(σ 2F + σ 2M)/σ 2P = δ 2A/δ 2P; heritability from male (h2M) =
4σ 2M/σ 2P = δ 2AM/δ 2P; and heritability from female (h2F) =
4σ 2F/σ 2P = δ 2AF/δ 2P (Singh and Chaudhary 1979).
99
sorghum crosses: 4031 × AS424, 675 × AS430, 675 × 3937
and 4567 × 654 flowered 8 days earlier than the untreated
control. The FOS-treated sorghum crosses had variable
plant height, ranging from 82.70 to 222.5 cm, with a
mean of 140.50 cm. The crosses that gained in plant
height because of FOS application were 3984 × AS430,
104 × 3993 and 3984 × AS424, measuring 158.5, 152.7
and 178.8 cm, respectively. Variation in seed yield and
hundred-seed weight was observed among F1 families,
with and without FOS. Mean grain yield plant−1 of 99.33,
99.73 and 154.8 g plant−1 was achieved in these FOStreated crosses: 4643 × AS436, 675 × 672 and 3424 × 630,
respectively. The yield response of these crosses was markedly higher than the Striga-resistant check, AS436, which
yielded 52.17 g plant−1. The mean hundred-seed weight
of 98 crosses increased from 0.09 to 1.44 g following FOS
treatment.
Treating sorghum seeds with FOS significantly
reduced the number of Striga per plant in the tested
population. A mean reduction of 13 Striga plants per
sorghum plant was recorded following FOS treatment.
The number of Striga plants was reduced in 99
sorghum crosses (Table 4). Only 1–2 Striga per plant
were found in the following crosses: 3424 × AS430,
1563 × 3937, 104 × 630, 3984 × 630, 3984 × AS426 and
AS435 × AS436. The resistant check, AS436, had a mean
of 4 Striga plants, as a result of seed treatment with FOS.
General combining ability effects of females
Results
Combined analysis of variance
The analysis of variance across locations showed highly
significant (P < .01) differences among the crosses for
both sorghum and Striga parameters (Table 3). Mean
squares were highly significant for females, males and
female × male interaction effects with and without FOS
application. Genotypes had significant interactions with
locations for grain yield, hundred-seed weight and
Striga count.
Response of crosses and checks to Fusarium
application
The mean values of the 100 crosses and 2 standard checks
for days to flowering, plant height, seed yield, hundredseed weight and the number of Striga plants with and
without FOS application across 3 locations are presented
in Table 4. Sorghum plots treated with FOS flowered significantly earlier than those that represented the untreated
control. The FOS treatment hastened flowering by 1–9
days, with a mean of 4 days. The following FOS-treated
The GCA effects of 10 female parents for sorghum and
Striga parameters are summarized in Table 5. The genotype 3984 had a relatively low GCA value for days to 50%
flowering, with and without FOS. Significant positive GCA
values for plant height was displayed by the genotype
3984 under FOS application. Only two female genotypes
AS435 and 4567 had significant GCA effects for grain
yield per plant and hundred-seed weight, with FOS treatment. Genotypes 3424 and 3984 displayed significant
negative and positive GCA effects for Striga count, in
that order.
General combining ability effects of males
The GCA effects of male parents for days to flowering,
plant height, seed yield, hundred-seed weight and
Striga counts, with and without FOS application, are presented in Table 6. Significant, positive and negative GCA
effects were observed for some of the evaluated genotypes, with and without inoculation. Genotype 3937
had low GCA value for days to flowering under FOS treatment. The genotypes 3993 had significantly large positive GCA effects for plant height. All tested male
100
E. MREMA ET AL.
Table 3. Mean squares and significance tests for seed yield per plant, days to flowering, plant height at 50% flowering, hundred-seed weight and number of Striga plants of 100 sorghum
hybrids derived from 10 × 10 North Carolina Design II and evaluated with (+) and without (−) F. oxysporum application in three locations in Tanzania.
Sorghum parametersb
SYP (g)
Sourcea
DF
+
DFL (d)
−
+
HFL (cm)
−
+
HSW (g)
−
+
NS*
−
+
−
Loc
2
1729.13**
2454.07**
116,933.92**
38,545.10**
2027.53**
1019.46**
14.60**
21.35**
35,290.51**
84,653.56**
Rep (Loc)
3
5.83**
26.56**
221.59*
309.07**
262.72**
164.13**
1.77**
1.27**
2.43
17.71
9
149.35**
165.72**
4958.92**
2234.51**
1181.62**
970.91*
2.78**
1.89**
935.04**
884.45**
GCAF
9
102.76**
114.16**
3361.30*
612.11**
525.66**
556.76**
2.12**
1.95**
2477.42**
3192.39**
GCAM
SCA
81
104.54**
107.33**
2271.78**
1184.85**
786.44**
747.08
2.86**
1.78**
567.63**
1254.55**
18
33.52**
29.49**
8565.46**
2960.94**
402.89**
297.40**
1.05**
1.01**
1171.08**
1419.31**
GCAF × Loc
18
37.33**
28.33**
1826.00**
1264.30**
538.78**
481.26**
1.92**
1.64**
2309.97**
3066.36**
GCAM×Loc
SCA×Loc
162
36.93**
42.68**
2119.17**
1268.31***
307.22**
239.38**
1.56**
1.16**
564.12**
1233.46**
Error
297
1.31
1.84
53.46
31.31
15.14
4.75
0.02
0.06
9.95
27.22
−0.09
0.34
54.48
−28.64
−13.04
−9.52
−0.04
0.09
95.49
96.89
EMSGCAM
2.24
2.92
134.36
52.48
19.76
11.19
−0.004
0.08
18.37
−18.51
EMSGCAF
51.62
52.75
1109.16
576.77
385.65
371.17
1.42
0.09
278.84
613.67
EMSSCA
12.52
13.3
17.24
16.54
13.45
11.77
9.06
9.48
10.97
5.76
SSGCAF %
8.61
9.16
11.68
4.53
5.98
6.75
6.93
9.82
29.07
20.77
SSGCAM %
SSSCA %
78.87
77.54
71.08
78.93
80.57
81.49
84.01
80.69
59.95
73.47
a
Loc, location; Rep (Loc), replications within locations; GCAF, general combining ability for females; GCAM, general combining ability for males; SCA, specific combining ability; GCAF×Loc, general combining ability for females ×
locations interaction; GCAM×Loc, general combining ability for males × locations interaction; SCA×Loc, specific combining ability × locations interaction; EMSGCAM, expected mean square for males; EMSGCAF, expected mean
square for females; EMSSCA, expected mean square for males × females; SSGCAF %, percentage sum of squares for general combining ability for females; SSGCAM %, percentage sum of squares for general combining ability for
males; SSSCA, %, percentage sum of squares for specific combining ability.
b
SYP, seed yield per plant; DFL, days to flowering; HFL, plant height at 50% flowering; HSW, hundred-seed weight; and NS number of Striga plants.
*, ** Significant at the 0.05 and 0.01 probability level, respectively.
Table 4. Mean comparison of seed yield per plant, days to flowering, plant height at 50% flowering, hundred-seed weight and number of Striga plants under artificial Striga infestation with
(+) and without (−) F. oxysporum application among sorghum hybrids evaluated at three locations in Tanzania.
SYPa (g)
Genotypes
HFLc (cm)
HSWd (g)
NSe (plant station)
+
−
t-Value
+
−
t-Value
+
−
t-Value
+
−
t-Value
+
−
t-Value
33.04
23.55
31.68
52.17
21.18
24.63
36.95
33.14
21.36
30.27
21.5
19.86
24.25
41.94
21.93
28.68
34.38
26
27.06
22.41
25.45
32.51
80.58
33.14
22.92
154.8
25.41
36.75
31.94
35.11
22.3
31.05
17.73
22.52
28.69
31.27
23.86
38.68
25.92
23.26
46.91
20.44
37.13
30.3
27.14
49.29
25.71
16.15
27.12
43.61
16.91
21.87
25.97
25.55
17.15
24.22
17.93
15.32
16.05
41.43
14.59
22.87
26.34
17.13
19.91
15.97
18.21
26.23
62.82
28.24
16.23
52.24
19.2
31.59
28.82
28.37
18.68
25.52
13.2
16
20.66
26.83
17.55
31.59
20.73
19.51
39.27
14.32
28.21
21.55
20.87
41.65
1.24
1.72
1.96
0.32
1.95
1.11
4.23***
1.29
1.59
2.81*
1.31
1.27
4.60***
0.16
3.19*
2.54*
0.5
3.18*
3.04*
4.85***
2.9**
1.57
0.77
1.56
1.67
0.62
3.85***
0.86
1.87
1.87
1.43
1.77
3.43**
5.21***
1.01
3.21**
1.29
1.44
0.75
2.41*
6.90*
2.82*
2.05
1.68
1.19
0.48
65.67
68.67
62.33
65.51
64
68.67
61.33
66.67
69.83
66.5
55.33
63.83
68
63
65.67
69.67
65.83
69.5
66
66.5
65.86
61.33
60.83
73.41
70.5
70
75
70
66.67
69
57.71
59.33
62.67
65.83
62.83
65.17
63.33
59.17
59.17
59
65.5
62.67
64.5
64.83
68.83
65.17
68.5
71.5
66
67.23
68.33
71.67
64.5
70.5
72.83
70.83
62.33
68.33
87.07
66.33
68.5
74.33
72.17
73.33
70.67
70.33
67.66
64.67
63.83
75.12
74.17
71.67
77
72.5
68.67
71.83
64.14
64.33
67.17
68.67
68
68
66.67
61.5
60.5
63.5
67.5
66.5
71.83
69.67
72.5
69.17
−1.16
−1.11
−1.44
−0.39
−0.94
−1.17
−0.68
−1.41
−1.49
−1.57
−2.62*
−2.37*
−0.66
−0.76
−0.38
−1.87
−1.32
−3.66***
−4.43***
−6.38***
−0.35
−4.47**
−1.03
−2.23
−1.16
−0.92
−2.24*
−2.61*
−0.29
−0.69
−1.71
−0.98
−0.94
−1.69
−0.91
−2.18
−0.51
−0.97
−0.48
−3.43**
−2.83
−3.46**
−3.79**
−2.48*
−1.12
−1.91
153.8
152.7
119.83
167.17
140.8
153.5
158.5
107
149.3
125.67
136.8
118.5
135.33
124.33
109.83
127.7
130.83
140.3
100.33
149.5
125.62
163.5
133
161.67
129.8
154.8
131.5
113.17
152.5
165.3
130.86
129.83
147.2
171
167.5
132.67
154.5
178.8
177.7
137.8
222.5
158.5
153.7
135.2
110
135.7
111.3
16.15
72.17
127.5
67.3
86.8
51.3
71.83
83
67.5
74.2
59.33
55.17
57
41.17
83.7
85.58
65.5
64
62.8
89.12
91.3
76.8
100
80
102
71.2
62.5
56.7
60
67.86
64.17
68
86.7
74.5
53.83
70.3
57.3
63.8
74.5
52
78.5
102.3
76
65.17
92.3
1.31
6.00***
6.79***
1.56
5.57***
2.61*
3.77**
4.13**
4.91***
2.11
2.73*
2.23
4.15**
5.10***
4.17**
1.81
2.38
4.00*
5.57***
5.35***
1.87**
5.85***
2.93*
2.34*
2.44*
2.33*
5.02***
3.68*
2.85*
3.94***
2.96*
4.73***
4.26**
3.52**
4.79***
5.05***
4.90***
8.80***
6.70***
3.41*
9.50***
3.44**
1.91
2.58*
4.69**
1.18
2.02
1.6
1.8
3.07
1.88
1.25
2.27
4.23
1.63
1.68
1.12
1.6
1.73
3.17
1.58
1.95
1.8
1.9
1.8
1.48
1.56
1.97
2.88
1.81
2
2.97
1.95
2.33
1.62
3.78
2.7
1.65
1.2
2.42
2.07
2.53
1.48
2.15
2.88
1.7
2.75
1.73
4.77
1.18
2.78
2.18
1.15
0.92
1.22
2.52
1.13
0.9
1.45
3.23
1.1
1.23
0.31
1.32
1.1
2.43
1.05
1.37
1.12
1.4
1.13
1.1
1.03
1.55
1.82
1.52
1.33
2.35
1.18
2.03
1.32
2.97
1.66
1.2
0.77
1.45
1.67
1.68
0.83
1.45
2.5
1.18
2.15
1.25
3.57
0.72
2.23
1.7
2.87*
2.74*
5.75***
6.21**
4.65***
4.87***
5.39***
0.54
4.91***
2.72*
3.64**
0.77
6.40***
6.15***
3.53**
1.75
1.85
2.02
2.1
1.42
3.52**
1.81
3.28*
1.75
4.74***
1.18
13.06***
0.81
2.83*
0.49
3.37*
1.35
3.45**
8.78***
1.78
6.10***
3.42**
2.69*
1.35
5.10***
8.49*
1.66
0.62
4.06***
1.53
4.36***
9.17
22.67
1.67
4.17
25.83
22.33
13
46.17
5.67
21
9.33
1.67
25.83
12
7.33
13
5.83
27
19.83
25.83
6.59
24
63.67
8.33
2.17
59.83
15.5
17.67
15.5
27.67
9.14
6.17
11.83
12.33
2.33
9.5
16
9.67
1.23
5.67
7
7.17
13.33
15.5
11.33
18.17
16
29.67
9.83
6.83
53.83
28
27.33
50.17
20.67
33.17
40.33
22.67
38.33
21.5
18.5
38.33
11.67
43.5
22.67
43.17
17.43
41.33
76
59.67
13.33
71.17
24
37.5
24.33
40.67
37
12.83
19.33
21.83
8.67
64
23.83
18.5
8.83
15
43.5
12.67
16.83
22.5
23.5
21
−1.13
−0.45
−0.59
−5.06
−1.61
−0.3
−1.94
−0.13***
−1.98
−0.84
−2.09
−1.24
−0.91
−4.41***
−2.95*
−1.27
−1.78
−0.79
−0.23
−0.83
−1.75
−0.87
−0.22
−2.05
−0.69
−0.22
−0.99
−0.99
−0.94
−0.6
−2.14
−2.18
−1.69
−2.09
−2.24*
−1.7
−0.53
−1.61
−2.95*
−5.35**
−20.25**
−1.91
−0.68
−0.86
−1.39
−0.52
101
(Continued )
ACTA AGRICULTURAE SCANDINAVICA, SECTION B — SOIL & PLANT SCIENCE
104*3937
104*3993
104*630
AS436
104*654
104*672
104*AS 430
104*AS424
104*AS426
104*AS429
104*AS436
1563*3937
1563*3993
1563*630
1563*654
1563*672
1563*AS426
1563*AS429
1563*AS430
1563*AS436
1563*AS424
3424*3937
3424*3993
Macia (104)
3424*AS430
3424*630
3424*654
3424*672
3424*AS424
3424*AS426
3424*AS429
3424*AS436
3984*3937
3984*3993
3984*630
3984*654
3984*672
3984*AS424
3984*AS426
3984*AS429
3984*AS436
3984*AS430
4031*3937
4031*3993
4031*630
4031*654
DFLb (d)
SYPa (g)
Genotypes
HFLc (cm)
HSWd (g)
+
−
t-Value
+
−
t-Value
+
−
t-Value
28.65
20.73
54.68
30.17
27.66
34.94
22.66
38.64
40.43
28.94
32.29
34.27
23.28
28.16
23.32
52.62
35.83
99.33
28.92
30.18
30.47
29.28
31.35
19.2
16.11
24.1
24.03
22.38
32.92
24.9
50.2
99.73
29.11
24.32
29.99
41.3
19.88
24.5
27.77
23.08
27.62
21.11
29.13
42.61
24.77
30.28
82.56
21.02
23.58
20.6
17.03
17.1
57.92
20.66
19.53
30.1
15.83
29.49
33.02
20.02
24.28
31.24
18.7
24.17
17.7
58.08
29.68
29.8
20.46
27.52
21.02
26.14
22.66
13.73
11.74
20
21.82
17.71
25.65
21.33
43.38
89.56
25.31
15.59
24.1
29.04
13.99
20
21
14.35
23.41
18.34
23.54
37.13
20.14
23.58
79.42
18.11
17.61
15.08
8.50***
1.66
−0.24
2.44*
2.79*
0.68
3.77**
1.04
2.81*
1.88
1.2
0.33
4.41***
1.88
1.26
−0.23
0.81
6.81***
3.67**
0.75
1.8
0.98
1.64
1.98
3.09*
0.7
1.64
1.35
1.18
0.62
0.31
5.48***
1.03
2.94*
1.03
2.25*
4.36***
4.92***
1.83
4.45***
0.63
0.7
29.13
0.53
0.86
3.95**
0.53
1.65
0.96
3.31**
66.5
69.83
58.67
71.33
64
65.83
61.33
66.83
61.17
62.5
70.33
62.33
63.83
68.17
56.83
61.67
64.67
70
64.17
66.33
65
71.83
65.33
65.5
59.67
62.67
64.33
62.5
68.33
68.17
61.17
62.33
71.5
70
66.83
60.17
59.67
54.67
67.5
60.5
67.17
56
66
67.67
67.67
63.17
65
64.17
71
68.17
72
79.17
60.17
74.83
68.83
70.67
66.17
69.83
65.33
66.33
73.5
69.5
69
73.67
60.33
65
69
74.17
65.5
72
67
74.67
68.33
67.5
68.17
67.83
72.17
64.17
71.67
71.33
65.17
67.67
74
74.83
72
67.83
66.67
57.67
71
64.33
73.33
57.67
67.83
72.5
71.17
66.67
69.17
66.83
74.5
71.67
−4.37***
−2.24*
−0.41
−1.39
−4.62***
−1.83
−1.64
−0.92
−3.22*
−1.35
−0.83
−1.77
−1.23
−2.54*
−0.63
−1.24
−1.82
−1.97
−0.81
−4.03**
−2.45*
−1.01
−1.9
−2.83*
−2.33*
−1.93
−6.31***
−0.91
−1.03
−1.1
−5.93***
−3.53**
−3.73**
−1.89
−3.97**
−3.22**
−1.5
−2.52*
−1.07
−1.29
−8.97***
−0.98
−2.31*
−1.31
−1.32
−1.45
−5.00***
−2.45*
−2.44*
−1.06
148.8
147
141.2
144.2
148.5
132.83
142.2
162.3
142
181.2
141
141.8
112.33
132.83
154.7
129.5
168.2
99.33
110
82.7
157
120.17
133.67
122
139.2
148.5
139.3
148.8
135.7
140.2
129
160.2
134.3
141
172.8
167.5
144
132.5
137.2
151.2
111.2
183.7
115.5
131
111.67
121.67
128.8
166.8
129.3
149.5
74
94.7
98.3
59.7
92.5
62
65.8
78.3
73.8
66.5
68.3
85.5
61.67
57.67
111
79
74.5
69
67.83
65
59.5
72.33
61
80.3
73.8
63
81.2
56
73.7
112.2
81.5
67.2
82
78.8
76.5
70.3
109.3
66.17
81.2
72.8
92.5
85.8
66.83
86.8
75.17
70.33
98.3
89.2
87
62.3
5.10***
2.36*
1.74
5.24**
1.95
3.66*
3.26*
3.53**
2.57*
8.50***
2.50*
1.91
5.10***
4.77***
1.75
1.72
5.2***
7.86***
3.82*
15.57***
4.36*
6.26***
2.72*
2.11
2.93*
4.64**
6.56***
6.01***
5.01***
0.97
2.71*
8.98***
6.87***
6.45***
10.77***
10.33***
1.23
3.25*
2.92*
4.09**
1.17
4.27**
2.09
2.74*
1.54
4.6**
1.19
4.83***
2.11
6.93***
+
4.2
1.52
2.28
1.62
1.52
2.07
1.77
1.73
4.81
1.95
2.43
2.8
1.65
1.55
1.75
1.85
2.367
2.43
1.62
2.35
2.48
2.4
2.02
2.85
1.35
1.57
1.67
1.88
1.47
1.25
2.12
2.4
1.55
1.63
2.42
2.12
2.88
2.25
2.32
1.677
2.6
1.9
1.73
2.67
2.22
1.98
2.23
1.67
1.82
1.45
−
2.95
1.15
1.83
1.05
1.32
1.13
1.3
1.32
3.37
1.03
1.06
1.92
1.22
1.12
1.4
1.93
1.783
2.05
1.28
1.733
2.03
1.63
1.7
2.3
1
1.27
1.72
1.28
1.17
0.75
1.7
1.47
1.23
2.02
1.7
1.45
1.55
1.22
1.73
1
2
1.78
1.43
1.52
1.65
1.37
2.02
1.15
1.38
1.12
NSe (plant station)
t-Value
+
−
t-Value
0.76
3.02*
2.37*
2.98*
0.95
2.97*
3.98**
2.43*
1.08
3.78*
7.77***
2.98*
5.54***
2.42*
1.24
−0.2
4.19**
0.87
4.61***
1.39
2.79*
5.28***
0.75
2.31
3.22**
1.06
1.07**
2.86*
2.01
1.92
0.88
5.67***
1.02
−0.38
5.03***
2.34
7.02***
5.44***
3.93**
2.25*
1.02
2.15
1.08
2.29*
2.07
4.87***
0.82
3.19*
1.13
2.43*
7.5
22.17
29.67
8.83
14.33
31.33
17.83
4.17
17
10.5
10
19.83
6.5
24.67
24.17
5.17
17.33
8.5
6.67
8.17
20.5
11.17
9
20
4
11.5
15
24.67
14.17
7.67
9.67
7.83
3.67
23
11.67
24.5
3.83
13.5
55.5
7.5
7.83
6.167
7.17
24.67
14
10.17
13.5
20
9.17
25.67
15.83
26.67
40
16
26.5
38.67
45.83
17.17
64.83
20
25.67
25.17
14
35.83
45.83
14.17
37
36.67
26.17
17
34.5
23.33
17.5
31.67
8.5
32.17
32.5
34
42.83
14.5
14.33
19.33
37.67
46.17
18.17
40.67
10.67
20.17
62.67
11.33
16.83
9.17
17.5
34.17
50.83
26.67
19.33
38
12.5
41.67
−1.95
−0.32
−0.43
−1.18
−2.63*
−0.34
−1.55
−3.17*
−1.42
−1.82
−1.37
−0.48
−3.38**
−0.67
−0.87
−4.71**
−1.36
−1.68
−2.34
−2.34*
−0.81
−3.74**
−1.57
−0.62
−5.58***
−1.27
−1.26
−0.71
−1.73
−2.42*
−1.57
−4.86***
−1.95
−1.36
−2.15
−0.81
−4.29**
−1.13
−0.15
−2.25*
−1.8
−1.82
−2.23
−0.52
−1.36
−1.36
−0.65
−1.07
−0.95
−0.86
E. MREMA ET AL.
4031*672
4031*AS424
4031*AS426
4031*AS429
4031*AS430
4031*AS436
4567*AS424
4567 *AS430
4567*3937
4567*3993
4567*630
4567*654
4567*672
4567*AS429
4567*AS436
4567*AS426
4643*AS429
4643*AS436
4643*3937
4643*AS426
4643*630
4643*654
4643*672
4643*AS424
4643*AS430
4643*3993
675*3937
675*3993
675*AS429
675*630
675*654
675*672
675*AS436
675*AS424
675*AS426
675*AS430
AS422 * 654
AS422*3937
AS422*3993
AS422*630
AS422*672
AS422*AS424
AS422*AS429
AS422*AS430
AS422*AS436
AS435*3937
AS435*3993
AS435*654
AS435*672
AS435*AS424
DFLb (d)
102
Table 4. Continued.
103
parents showed significant positive and negative GCA
effects for seed yield. Notably, genotypes 3933, 672
and AS426 had significantly large, positive GCA values
for grain yield, with and without FOS application. Genotypes 672, 3937, AS436 and AS426 displayed large negative GCA effects for Striga count. This was contrary to
genotype 3993 with significant positive GCA.
14.33
16.67
31.17
4.17
2
24.62
15.10
24.69
17.14
***
63.67
1.23
46.17
31.83
42.5
7.5
9.33
42.14
28.82
22.92
24.15
***
76
6.83
−1.82
−1.16
−0.44
−3.7**
−2.59*
−0.85
ACTA AGRICULTURAE SCANDINAVICA, SECTION B — SOIL & PLANT SCIENCE
AS435*AS426
30.16
21.98
1.39
65
68.33
−6.74***
156.8
AS435*AS429
22.02
17.73
1.44
65.17
67.33
−2.32*
134.8
AS435*AS430
25.04
19.63
3.17*
66.17
68.67
−1.4
105.67
AS435*630
17.03
12.13
4.81**
68.33
74
−1.39
112
AS435*AS436
23.46
16.56
1.96
64.33
70.67
−2.41*
135.8
AS422*AS424
21.67
17.05
3.21**
68.27
72.54
−1.03
143.54
Cross mean
32.69
25.12
65.08
69.16
140.50
CV (%)
12.78
8.89
1.76
1.97
5.23
LSD (0.05)
23.31
20.22
9.23
10.097
76.88
F-Test
***
***
***
***
***
Maximum
154.80
89.56
75.00
87.07
220.50
Minimum
16.11
11.74
54.67
57.67
82.70
Note: Bolded values indicate the checks, high yielding and Striga resistant families with FOS application.
a
SYP, seed yield per plant.
b
DFL, days to flowering.
c
HFL, plant height at 50% flowering.
d
HSW, hundred-seed weight.
e
NS, number of Striga plants.
*, **, *** Significant at the 0.05, 0.01 and 0.001 probability level, respectively.
85.3
69
71.17
77.33
87.5
71.42
74.90
7.5
54.01
***
127.5
16.15
3.24**
3.65*
6.28***
1.22
4.28**
6.54**
2.267
1.78
1.83
1.55
2
1.24
2.10
7.23
1.63
***
4.81
1.22
1.48
1.05
1.45
1.12
1.52
1.15
1.52
16.15
1.52
***
3.57
0.31
3.14*
3.11*
1.58
5.87***
1.48
2.34*
Specific combining ability effects
Estimates of the SCA effects of the 100 sorghum crosses
averaged across three test locations for days to
flowering, plant height, seed yield, hundred-seed weight
and the number of Striga plants are presented in Table 7.
Sorghum crosses had negative and positive SCA effects
for the tested parameters under FOS treatment. Treatment
of sorghum seeds with FOS contributed to significantly
low negative SCA values for days to flowering in 3424 ×
AS429 and 104 × AS436. Families of crosses 104 × AS424
and 4567 × 3937 had significant and relatively large SCA
values for hundred-seed weight when treated with FOS.
Relatively large, positive SCA values were recorded for
grain yield in the following crosses: AS435 × 3993, 675 ×
672 and 4643 × AS436 when treated with FOS. The newly
developed sorghum crosses had relatively low SCA
values for the number of Striga plants. This was recorded
in the families of 4567 × AS429, 3424 × AS436 and
3424 × AS430, following FOS application.
Estimates of genetic variance components
Estimates of genetic variance components and contribution of sorghum genotypes and their interaction to
total variance with and without FOS are presented in
Table 8. Significant differences in variances between
treatments with and without FOS were observed for
days to flowering, plant height at flowering, grain yield
per plant, hundred-seed weight and number of Striga
per plant with and without FOS application.
Discussion
Combined analysis of variance
Expression of heterosis and transgressive segregation
following hybridization depends on the levels of recombination of the loci that control traits of interest (Acquaah
2009). Superior parents harboring multiple additive-effect
genes for economic traits could be useful for trait
advancement through recurrent selection cycles. In this
study, significant differences for the recorded traits were
observed among tested families (Table 3). This could
imply the existence of substantial genetic variability
104
E. MREMA ET AL.
Table 5. Estimates of the general combining ability effects of 10 sorghum genotypes used as female parents for days to flowering, plant
height at flowering, seed yield per plant, hundred-seed weight and number of Striga with (+) and without (−) F. oxysporum dressing in
three locations.
SYPa (g)
DFLb (d)
HFLc (cm)
HSWd (g)
NSe
Female
+
−
+
−
+
−
+
−
+
−
104
1563
3424
3984
4031
4567
4643
675
AS422
AS435
−3.36***
−3.90***
2.31**
−3.17***
2.97***
1.38
3.38***
6.79***
−4.88***
−1.52
−3.04**
−4.12***
6.07***
−2.93**
2.56*
2.35*
−2.62*
6.45***
−4.00***
−0.72
−0.09
1.39
1.05
−2.46
0.96
−1.50
0.53
0.54
−1.48
1.06
−0.42
2.76***
0.17
−3.31***
1.75
−1.25
0.30***
0.97*
−1.64
0.67*
−0.23
−13.79***
0.41
24.80***
−0.31
3.97
−11.94***
6.86
−3.87
−5.90*
−3.97*
−7.79**
−0.87
−6.18***
7.57***
0.63
−5.50***
3.82*
6.67***
5.62***
−0.14***
−0.25***
0.29***
0.00***
0.32***
0.14***
0.05***
−0.24***
0.06***
−0.23***
−0.25
−0.20
0.23***
−0.02
0.25
0.05
0.16
−0.06
−0.01
−0.15
2.40
−0.77
8.85***
−7.01**
1.93
−1.30
−3.60
−1.10
1.20
−0.60
2.17
−0.95
9.09*
−5.11
−3.98
2.13
−2.28
1.29
−1.18
−1.18
a
SYP, seed yield per plant.
DFL, days to flowering.
HFL, plant height at 50% flowering.
d
HSW, hundred-seed weight.
e
NS, number of Striga plants.
*, **, *** Significant at the 0.01 and 0.001 probability level, respectively.
b
c
additive and non-additive gene effects, respectively
(Makanda et al. 2009; Konate et al. 2017). Generally,
non-additive gene effects contributed more favorable
genes towards high values of the studied traits. This
suggested the possibilities of using hybridization for
sorghum yield improvement and Striga management.
contributed by the male and female parents used as well
as differential gene interaction within the different
crosses generated. This genetic variation is useful for subsequent selection and genetic gains.
Significant genotypes × locations interactions were
detected for grain yield, hundred-seed weight and
Striga count (Table 3). This indicates that the superiority
of genotypes could only be assessed from multiple
location testing (Abakemal et al. 2016). Also, grain yield
and seed weight are complex traits whose expression
is greatly conditioned by genotype × environment interaction. This suggests the need for continuous selection
of potential sorghum genotypes across several sites to
identify stable and location-specific genotypes. The significant values of the GCA mean squares of females
and males and the SCA mean squares for females ×
males interaction indicated the importance of both
Response of families and checks to F. oxysporum
Improved agronomic performances were observed
among the tested sorghum genotypes for plant height,
seed yield per plant and hundred-seed weight under
Striga infestation with FOS treatment when compared
with controls, i.e. Striga infestation without FOS (Table
4). This suggested that FOS significantly reduced the
impact of Striga and boosted sorghum productivity.
This was accompanied by a reduction in the number of
Table 6. Estimates of the general combining ability effects of 10 sorghum genotypes used as male parents for days to flowering, plant
height at flowering, seed yield per plant, hundred-seed weight and number of Striga with (+) and without (−) F. oxysporum dressing
evaluated in three locations.
SYPa (g)
DFLb (d)
HFLc (cm)
HSWd (g)
NSe
Male
+
−
+
−
+
−
+
−
+
−
3937
3993
630
654
672
AS424
AS426
AS429
AS430
AS436
−2.25**
5.60***
−3.82***
−0.72
3.71***
−5.31***
2.51**
−3.09***
−1.22
4.59***
−2.14*
4.17***
0.64
0.31
3.39***
−4.92***
5.02***
−2.80**
−2.60**
−1.07
−2.44
−0.16
0.94
0.43
1.79
−0.07
0.06
0.65
−0.49
−0.71
−2.33
0.81
0.35
0.27
1.88
−0.58
−0.38
0.50
0.05
−0.57
−1.80
7.15**
−2.23
−4.79
−5.58*
4.91
4.95
−3.43
0.11
0.71
−2.33
0.81
0.35
0.27
1.88
−0.58
−0.38
0.50
0.05
−0.57
0.30***
−0.12***
0.13**
0.11***
0.06***
−0.02***
0.16***
−0.24
−0.19
−0.19
0.22
−0.18
0.07
−0.04
0.07
0.16
0.24
−0.21
−0.19
−0.14
−3.05
10.29***
−1.58
−1.20
−3.60
4.00
−1.88
−0.12
−0.78
−2.08
−0.08
6.92
−5.91
0.56
−6.36
2.43
−2.78
2.24
−4.18
7.16
a
SYP, seed yield per plant.
DFL, days to flowering.
HFL, plant height at 50% flowering.
d
HSW, hundred-seed weight.
e
NS, number of Striga plants.
*, **, *** Significant at the 0.05, 0.01 and 0.001 probability level, respectively.
b
c
ACTA AGRICULTURAE SCANDINAVICA, SECTION B — SOIL & PLANT SCIENCE
105
Table 7. Estimates of specific combining ability effects of 100 sorghum hybrids for days to flowering, plant height, seed weight per
plant, hundred-seed weight and Striga count with (+) and without (−) F. oxysporum (FOS) evaluated in three locations.
SYPa (g)
Cross
104*3937
1563*3937
3424*3937
3984*3937
4031*3937
4567*3937
4643*3937
675*3937
AS422*3937
AS435*3937
104*3993
1563*3993
3424*3993
3984*3993
4031*3993
4567*3993
4643*3993
675*3993
AS422*3993
AS435*3993
104*630
1563*630
3424*630
3984*630
4031*630
4567*630
4643*630
675*630
AS422*630
AS435*630
104*654
1563*654
3424*654
3984*654
4031*654
4567*654
4643*654
675*654
AS422*654
AS435*654
104*672
1563*672
3424*672
3984*672
4031*672
4567*672
4643*672
675*672
AS422*672
AS435*672
104*AS424
1563*AS424
3424*AS424
3984*AS424
4031*AS424
4567*AS424
4643*AS424
675*AS424
AS422*AS424
AS435*AS424
104*AS426
1563*AS426
3424*AS426
3984*AS426
4031*AS426
4567*AS426
4643*AS426
675*AS426
DFLb (d)
HFLc (cm)
HSWd (g)
NSe
+
−
+
−
+
−
+
−
+
−
7.56
−5.08
1.36
−7.95
5.31
10.22
−3.31
−11.61
0.54
2.96
−9.78
−8.55
41.57
−11.01
−9.37
−9.12
−15.98
−21.11
−4.04
47.38
7.77
18.57
−14.10
4.59
−3.10
3.65
−0.18
−9.16
0.69
−8.72
−5.83
−4.54
−7.27
4.06
15.94
2.53
−4.48
13.03
−5.61
−7.83
−6.82
−2.23
−0.37
−7.79
−9.14
−12.9
−6.85
58.12***
−2.31
−9.71
10.72
3.57
3.85
16.06*
−8.03
−4.49
−9.97
−8.26
0.21
−3.66
−8.88
4.67
−0.81
−4.52
18.10*
17.65*
−6.81
−10.41
6.00***
−3.32***
−2.60**
−6.62***
2.89**
7.91***
0.33
−7.38***
1.25
1.54
−9.88***
−8.90***
27.68***
−10.14***
−10.08***
−11.41***
−6.45***
−17.81***
−4.07***
51.06***
4.62***
20.00***
20.63***
−1.95*
−7.24***
−3.62***
−1.90***
−10.66***
−7.19***
−12.70***
−5.25***
−6.50***
−12.07***
4.56***
13.88***
3.68***
3.56***
11.73***
−7.21***
−6.38***
−3.37***
−1.30
−2.77**
−7.80***
−13.82***
−11.94***
−3.00**
54.83***
−0.87
−9.96***
8.61***
2.34*
2.77**
14.54***
−5.45***
−6.51***
−3.63***
−10.84***
2.36*
−4.19***
−9.73***
0.53
−7.62***
−6.26***
25.43***
25.80***
0.22
−12.27***
3.21
−0.12
−2.27
2.58
0.99
0.11
1.09
1.24
−6.40
−0.44
3.93
1.77
−5.05
3.45
−0.96
−0.84
−2.69
−2.87
4.15
−0.89
−3.51
−4.33
3.02
−0.64
1.94
5.89
−1.46
1.70
−3.95
1.34
−1.33
−1.14
8.54
2.21
−1.21
−1.60
5.89
−4.79
−4.27
−2.31
1.98
1.49
2.17
−1.00
−1.24
−1.46
−1.98
−4.99
1.87
3.16
1.84
−0.45
0.70
−3.29
3.95
−2.1
0.05
4.54
−7.44
2.19
4.86
−0.62
2.89
−3.43
−7.35
−1.9
0.74
1.23
2.13
−1.21
−2.28
3.70
3.28
−0.20
−1.59
4.42
−7.47
−0.78
1.99
14.39**
−6.26
2.06
−2.02
−2.34
−2.40
−6.72
2.72
−1.42
−3.05
−5.89
2.04
1.89
1.27
5.28
−2.77
0.90
−3.49
3.87
−0.64
−3.64
7.45
1.93
−1.98
1.37
4.98
−5.18
−1.07
−3.22
1.09
0.57
1.33
−1.02
−0.77
−0.75
−2.97
−4.30
3.97
2.83
2.38
−3.63
−0.03
−3.72
8.87*
−1.11
−1.34
5.33
−9.22*
2.47
4.51
0.68
2.93
−4.92
−10.34**
−2.49
2.96
2.29
15.81***
−5.93*
24.88***
−15.82***
15.79***
−0.18
−16.28***
−5.78*
−1.85
−10.64***
5.76*
1.95
−14.58***
−0.97
−11.67***
30.06***
13.27***
−5.23*
−6.11*
−12.47***
−17.73***
0.34
16.61***
4.92
−27.48***
−0.75
31.16***
−4.45
17.28***
−19.88***
5.80*
−11.61***
−4.13
−27.36***
0.78
2.61
−3.12
−13.09***
12.64***
37.48***
19.29***
7.05*
−21.67***
−4.74
14.67***
−26.07***
11.17***
18.90***
−19.37***
0.77
−37.70***
−5.52*
7.16**
9.07**
2.37
−6.70*
−10.99***
−10.79***
42.64***
10.47***
4.56
−0.35
19.93***
7.93**
−3.46
−19.43***
−50.33***
20.97***
36.11***
−12.04***
13.02***
−4.97**
15.57***
−5.99***
−5.83***
−1.77
−19.66***
−14.44***
−47.46***
−4.62**
10.09***
25.30***
0.85
−1.71
0.92
−15.40***
6.94***
25.10***
0.04
−11.31***
26.77***
4.58**
−18.50***
−8.43***
−11.10***
32.29***
−9.97***
−4.39**
−5.09**
−27.41***
−4.29**
−16.35***
8.36***
8.51***
1.47
1.32
26.26***
7.22***
16.10***
16.82***
−11.30***
1.81
−8.24***
−13.63***
−8.17***
−11.28***
11.16***
6.71***
1.53
22.64***
−16.69***
−10.78***
12.86***
−9.09***
11.53***
0.72
4.8688
−17.58***
10.18***
16.58***
−15.92***
−6.81***
13.94***
1.58
−6.29***
−4.11**
−0.22*
−0.55***
−0.71***
−1.19***
2.06***
2.28***
−0.82***
−0.48***
−0.20
−0.17
−0.23*
−0.01
0.61***
0.45***
−1.12***
−0.16
−0.46***
0.15
0.29**
0.49***
−0.27**
1.19***
0.46***
−0.15
0.24*
0.08
0.21*
−0.73***
−0.60***
−0.43***
−0.17
−0.38***
−0.54***
0.33**
−0.34***
0.46***
0.15
0.16
0.62***
−0.29**
−0.78***
0.02
−0.13
−0.69***
1.71***
−0.66***
−0.20*
0.47***
0.37***
−0.12
2.31***
−0.27**
−0.74***
0.08
−0.87***
−0.43***
0.73***
−0.20
−0.22*
−0.38***
−0.48***
−0.21*
1.24***
0.63***
−0.29**
−0.54***
0.05
0.41***
1.15
0.92
1.22*
1.13***
0.90***
3.23***
1.10***
1.23
1.45**
0.31
1.32
1.10
2.43
1.05
1.37
1.03*
1.12
1.40
1.13*
1.10***
1.55
1.82***
2.35**
1.18
2.03*
1.32***
2.97
1.66***
1.33***
1.20
0.77
1.45
1.67**
1.68
0.83
1.45*
2.50
1.18
1.25
2.15
3.57*
0.72
2.23
1.70***
2.95***
1.15*
1.83
1.05
1.32*
1.13
3.37***
1.03*
1.06***
1.92
1.22***
1.30*
1.93**
1.12*
1.32
1.40*
1.28*
1.27*
2.03***
1.63***
1.70
2.30
1.733
1.78
−5.47*
−9.77***
2.92
6.60**
−0.84
6.06**
−1.97
3.86
0.07
−1.47
−5.30*
1.05
29.25***
−6.23**
−12.00***
−13.77***
−10.47***
0.20
28.74***
−11.47***
−14.43***
−0.91
37.28***
−4.36
−4.30
−2.40
10.40***
−4.93*
−7.40***
−8.93***
9.34***
−5.96**
−7.43***
2.43
2.15
7.04**
0.68
−3.32
−11.45***
6.51*
8.24***
2.11
−2.86
11.33***
−6.12**
−3.89
0.91
−2.76
−5.05*
−1.92
24.49***
−11.9***
−12.63***
−2.60
0.96
−0.15
4.32
4.82*
−14.31***
6.99**
−10.14***
−6.78**
5.42*
−5.16*
14.33***
−6.94**
−1.64
−0.64
16.00***
29.67*
9.83
53.83
28.00*
50.17***
20.67
33.17
27.33*
40.33
22.67*
38.33
21.50***
18.5*
38.33**
17.43***
11.67
43.50
22.67***
43.17***
41.33***
76.00
71.17***
24.00**
37.50
24.33
40.67***
37.00**
13.33**
12.83***
19.33***
21.83**
8.67***
64.00***
23.83
18.50
8.83
15.00***
12.67***
43.50**
16.83
22.50***
23.5
21.00
15.83
26.67**
40.00
16.00
26.50
38.67*
64.83***
20.00***
25.67***
25.17*
14.00
45.83***
14.17
35.83***
17.17***
45.83**
26.17*
32.17***
34.50
23.33***
17.50***
31.67***
17.00
37.00*
(Continued )
106
E. MREMA ET AL.
Table 7. Continued.
SYPa (g)
Cross
+
DFLb (d)
−
+
HFLc (cm)
−
+
AS422*AS426
−7.06
−8.87***
4.69
5.45
2.44
AS435*AS426
−1.93
−7.23***
−1.12
−1.08
17.74***
104*AS429
5.63
5.16***
0.95
1.63
−10.69***
1563*AS429
1.89
−0.85
2.47
0.96
17.51***
3424*AS429
−8.02
−9.49***
−8.97
−5.64
−6.13*
3984*AS429
−1.58
0.35
−4.18
−2.8
−23.58***
4031*AS429
−0.81
−4.00***
4.73
3.45
7.92**
4567*AS429
−1.21
−0.28
4.02
5.31
−7.72*
4643*AS429
4.44
10.21***
−1.49
−0.91
43.56***
675*AS429
−1.88
−2.90**
2.15
1.09
−7.75**
AS422*AS429
6.00
5.45***
1.84
−0.14
−17.22***
AS435*AS429
−4.47
−3.65***
−1.53
−2.95
4.12
104*AS430
10.44
6.71***
−3.08
−4.25
18.60***
1563*AS430
1.09
1.73
0.10
−1.25
−26.01***
3424*AS430
−9.26
−12.14***
4.95
4.84
−10.74***
3984*AS430
−6.27
−5.05***
0.63
0.67
−6.43*
4031*AS430
−5.19
−5.33***
−1.46
−2.11
8.68**
4567*AS430
7.40
4.84***
3.82
1.91
18.20***
4643*AS430
−17.15
−7.93***
−5.36
−1.30
11.01***
675*AS430
4.63
0.29
−4.87
−2.31
20.51***
AS422*AS430
17.62*
18.84***
4.68
4.98
−5.26*
0.61
−1.17
−28.56***
AS435*AS430
−3.31
−1.95*
104*AS436
−10.84
−2.86**
−8.86
−5.80
−3.70
1563*AS436
−9.37
−3.74***
0.82
−0.98
22.53***
3424*AS436
−6.94
−4.38***
−6.00
−4.39
−11.30***
3984*AS436
14.40
18.37***
3.68
2.26
56.98***
4031*AS436
−3.71
3.71***
0.59
0.35
−7.59**
4567*AS436
−13.73
−8.48***
−5.96
−6.97
10.01***
4643*AS436
60.27***
8.59***
5.19
5.32
−29.45***
675*AS436
−13.36
−4.97***
6.68
4.48
−13.29***
AS422*AS436
−6.03
0.31
4.87
4.26
−25.19***
1.45
0.98
AS435*AS436
−10.7
−6.55***
−1.01
a
SYP, seed yield per plant.
b
DFL, days to flowering.
c
HFL, plant height at 50% flowering.
d
HSW, hundred-seed weight.
e
NS, number of Striga plants.
*, **, *** Significant at the 0.05, 0.01 and 0.001 probability level, respectively.
Striga plants observed under FOS application (Table 4).
Interestingly, some evidence of successful transfer of
genes for Striga resistance and FOS compatibility was
revealed through some superior progenies obtained
from crosses between the FOS incompatible line AS435
and its compatible male counterparts. For instance, the
cross AS435 × 3993 had above-average seed yield and
hundred-seed weight. Therefore, seed yield could be
improved significantly through hybridization and continuous directed selection.
A tall plant is associated with improved total biomass
production, which is one of the most important farmerpreferred attributes in sub-Saharan Africa (Kriegshauser
et al. 2006). Therefore, these genotypes can be grown
for both human consumption and livestock feed under
FOS biocontrol in Striga-infested farming systems in the
semi-arid regions of Tanzania. Farmers could also adopt
the crosses 675 × 672, 4643 × AS436 and 3424 × 630
with improved productivity under FOS application
because they out-yielded the resistant check AS436.
These hybrids are useful genetic stocks for further selection and progeny evaluation. Marked differences in the
HSWd (g)
NSe
−
+
−
+
−
−12.04***
2.89
3.79*
5.61***
1.06
13.01***
−15.55***
−10.64***
12.32***
2.21
−7.52***
−4.29**
−19.40***
−2.81
6.20***
10.01***
10.26***
3.00
4.63**
−8.18***
5.46***
−9.12***
4.19***
−3.40*
−8.94***
−15.80***
−19.56***
36.39***
0.51
4.20**
−5.49***
7.90***
−1.07***
0.25*
−0.03
0.29**
0.56***
−0.15
−0.55**
−0.44**
0.47**
−0.14
−0.18
0.16
0.51***
0.13
−0.19
−0.17
−0.70***
−0.31**
−0.60***
0.46***
0.71***
0.16
−0.62***
−0.19
−0.54***
0.85***
−0.15
−0.29**
0.48***
−0.11
0.26**
0.33**
1.00***
2.05
1.72
1.28
0.75
1.70
1.47**
2.02
1.70
1.17
1.45
1.23
1.22*
1.73
1.00
1.55
2.00
1.78
1.15**
1.43
1.52
1.65
1.37***
2.02
1.12*
1.15***
1.38**
1.12
1.48**
1.05
1.45
1.52
10.02***
1.52
3.43
12.63***
−14.88***
−2.49
−8.27***
10.8***
5.76**
0.10
−9.19***
2.10
−3.90
6.12**
−21.18***
−0.32
−2.11
−9.03***
−6.90**
11.10***
8.97***
17.27***
−6.27**
13.42***
−15.91***
0.81
16.20***
12.27***
−1.10
−8.43***
−0.40
−10.60***
8.50***
36.67***
32.50
34.00***
14.50
14.33**
19.33**
46.17
18.17*
42.83**
40.67***
37.67
20.17
62.67
11.33***
10.67
16.83
9.17*
42.14***
17.50***
34.17**
50.83***
26.67
19.33*
7.50***
38.00***
12.50
41.67***
46.17
31.83
42.50***
9.33***
genetic constitution of the sorghum crosses contributed
to the observed variation in seed yield and hundred-seed
weight.
Combining ability effects
The present study recorded significant negative and
positive GCA effects for measured traits, indicating that
additive and non-additive gene action are involved in
their expression. Genetic advance from selection for
enhanced yield and adaptability can be realized from
populations developed from genotypes such as the
male parent 3937 and female parents 675 and 4643.
The GCA values of these parents were low for days to
flowering with and without FOS treatment. Early
flowering and early maturity are escape mechanisms
against terminal drought and heavy Striga infestation,
which typically occur during the late stages of plant
development (Badu-Apraku et al. 2014). Male parents
that had low GCA values in the desirable direction for
the number of Striga plants (672, 3937, AS436 and
AS426) were good general combiners and useful for
ACTA AGRICULTURAE SCANDINAVICA, SECTION B — SOIL & PLANT SCIENCE
107
Table 8. Estimates of variance components for yield and yield-related traits, and Striga count of 100 sorghum hybrids derived from a
10 × 10 North Carolina Design II and evaluated with (+) and without (−) F. oxysporum application in three locations in Tanzania.
Sorghum parameters
SYPb (g)
a
Parameter
+
DFLc (d)
−
+
HFLd (cm)
−
+
HSWe (g)
−
+
NSf
−
+
−
0.45
0.58
26.87*
10.50
3.95
2.24
−0.001
0.001
3.67
−3.70
δ 2GCAF
−0.02
0.07
10.90
−5.73
−2.61
−1.90
−0.01
0.002
19.1*
19.38*
δ 2GCAM
2
0.43
0.65
37.77
4.77
1.34
0.34
−0.01
0.003
22.77
15.68
δ GCA(GCAF+GCAM)
2
5.16**
5.27**
110.92**
57.68**
38.57**
37.12**
0.14
0.09
27.88**
61.37**
δ SCA
1.31
1.84
53.46*
31.31*
15.14
4.75
0.02
0.06
9.95
27.22
δ 2W (Error)
0.08
0.12
0.34
0.08
0.03
0.01
−0.08
0.03
0.82
0.26
δ 2GCA/δ 2SCA
0.86
1.30
75.54
9.54
2.68
0.68
−0.02
0.01
45.54
31.36
δ 2A
2
20.64**
21.08**
443.68
230.72
154.28
148.48
0.56
0.36
111.52
245.48
δD
4.90
4.03
2.42
4.92
7.59
14.78
−5.29
6.00
1.56
2.80
(δ 2D/δ 2A)1/2
−0.08
0.28
43.60
−22.92
−10.44
−7.60
−0.04
0.01
76.40
77.52
δ 2AM
2
1.80
2.32
107.48
42.00
15.80
8.96
0.004
0.004
14.68
−14.80
δ AF
−14.6**
−14.62**
−317.07**
−146.5**
−101.91**
−106.95**
−0.01
−0.22
−96.46**
−172.57**
δ 2EW
6.69
7.44
183.27
91.38
54.38
42.04
0.15
0.15
49.22
96.43
δ 2T
0.13
0.17
0.41*
0.10
0.05
0.02
–
0.07
0.93**
0.33
H2 (δ 2A/δ 2T)
2 2
2
–
0.04
0.24
–
–
–
–
0.07
1.55**
0.80**
HM(δ AM/δ T)
2 2
2
0.27
0.31
0.59*
0.46*
0.29
0.21
0.03
0.03
0.30
–
HF(δ AF/δ T)
a 2
δ GCAF, additive variance of female; δ 2GCAM, additive variance of male; δ 2GCA, additive variance of female and male; δ 2SCA, additive variance for female and male
interaction; δ 2A, additive variance in the population; δ 2D, dominance variance; δ 2AM, additive variance in males; δ 2AF, additive variance in female; δ 2EW, environmental
variance; δ 2T, Total variance; H2, broad sense heritability; H2M, heritability due to males; H2F, heritability due to female effects.
b
SYP, seed yield per plant.
DFL, days to flowering.
d
HFL, plant height at 50% flowering.
e
HSW, hundred-seed weight.
f
NS, number of Striga plants.
*, ** Significant at the 0.05 and 0.01 probability level, respectively.
c
breeding for Striga resistance. The male parents 672 and
3933; and female parents 675 and 4643 with large and
positive GCA values for grain yield, with and without
FOS application, should be useful for accumulating
genes for consistent productivity under Striga infestation, with the aid of FOS application. These parents
might possess unique genes conditioning Striga resistance and FOS compatibility. Tall sorghum genotypes,
such as 3984, 675 and 4567, are highly preferred by
growers in Tanzania for grain and stalk feed.
Non-additive gene action, i.e. dominance, over-dominance and epistasis, among cross progenies are reflected
by the extent of the SCA effects. These genetic parameters are important for hybrid breeding (Acquaah
2009). There is great potential to develop superior F1
hybrids or to select transgressive segregants in the F2
or subsequent generations because some cross progenies evaluated had significant positive SCA effects for
grain yield under FOS treatment.
Therefore, the present study showed that both FOS
treatments and locations influenced the expression of
the studied traits. Additive and non-additive gene
effects influenced genetic variation for seed yield per
plant, hundred-seed weight, height at flowering, days
to flowering and Striga number for sorghum crosses
evaluated across three semi-arid locations in Tanzania.
Application of FOS increased the contribution of additive
and non-additive genetic effects, raising the possibility of
breeding for Striga-resistant sorghum genotypes that are
FOS compatible. Crosses 675 × 672, AS435 × 3993 and
4643 × AS436 displayed large SCA effects for grain
yield, whereas 3424 × AS430, 4567 × AS429 and 3424 ×
AS436 had small SCA effects for SN. These crosses are
recommended for further breeding or production in
the three Striga-infested test locations or similar agroecologies using FOS as a biological control agent.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
The study was funded by the Alliance for Green Revolution in
Africa (AGRA) through the African Centre for Crop Improvement of University of KwaZulu-Natal.
Notes on contributors
Emmanuel Mrema is a PhD holder of Plant Breeding graduated
at University of KwaZulu-Natal, African Centre for Crop
Improvement, Cereal and Vegetable Breeder at Tanzania Agricultural Research Institute, Tumbi Center, Tabora, Tanzania.
Hussein Shimelis is Professor of Plant Breeding at University of
KwaZulu-Natal, African Centre for Crop Improvement, and is the
Deputy Director of African Centre for Crop Improvement.
Mark Laing is Professor of Plant Pathology at University of
KwaZulu-Natal, African Centre for Crop Improvement, and is
the Director of African Centre for Crop Improvement.
108
E. MREMA ET AL.
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