Table 1. Qualitative and quantitative traits of cowpea assessed during the study.
No
|
Trait
|
Abbreviation
|
Trait description
|
Qualitative traits
|
1
|
Flower colour
|
FLC
|
Flower colour intensity: violet-1, yellow -2, white- 3
|
2
|
Leaf green colour
|
LGC
|
Colour intensity: light-1, medium -2, dark- 3
|
3
|
Growth pattern
|
GTH
|
Type 1 - determinant, type 2- indeterminate, type 3- creeping
|
4
|
Pod colour
|
PDC
|
Pod colour intensity; light green-1, deep green -2, purple- 3
|
5
|
Seed coat colour
|
STC
|
Primary colour intensity of the seed coat; reddish- brown -1, white -2, purplish- brown -3, brown - 4, black - 5,
|
6
|
Leaf size
|
LFS
|
Size of the most tip leaf ; small -1, medium -2, big -3
|
Quantitative traits
|
1
|
Days to 50% flowering
|
DTF
|
The number of days from sowing until 50% of the plants in a plot have visible flowers
|
2
|
Days to 90% maturity
|
DTM
|
Days from date of sowing to the date when 90% of pods in a plot turn yellowish brown
|
3
|
Number of pods per plant
|
NPP
|
Mean number of mature pods from 10 randomly selected and tagged plants in a plot
|
4
|
Pod length
|
PDL
|
Mean length of 10 mature pods from randomly selected and tagged plants
|
5
|
Number of seeds per pod
|
NSP
|
Mean weight of seed from mature pods of 10 randomly selected and tagged plants
|
6
|
Seed size
|
SDS
|
Mean length of 10 randomly selected seed measured in millimetres
|
7
|
Hundred seed weight
|
HSW
|
Weight of one hundred randomly selected seeds of a genotype measured in grams
|
8
|
Grain yield
|
GYD
|
The average grain yield per plot and converted into kg ha-1 using the formula given above.
|
Table 2. Mean squares and significant tests among 100 cowpea germplasm collections evaluated based on eight quantitative agronomic traits in two locations in Zambia.
Source of variation
|
DF
|
DTF
|
DTM
|
PDL
|
NPP
|
NSP
|
SDS
|
HSW
|
GYD
|
Location (L)
|
1
|
702.20*
|
13806.30***
|
542.61***
|
2550.25***
|
29.7
|
0.01
|
6.30
|
107770.00
|
Rep(R)
|
2
|
8.30
|
1731.08***
|
56.94**
|
20.91
|
1.72
|
2.40
|
0.67
|
388357.00
|
Block (B)
|
18
|
196.90
|
167.30
|
8.84
|
61.44
|
14.77*
|
5.09*
|
13.25*
|
1070734.00***
|
Genotype (G)
|
99
|
242.50*
|
154.70*
|
14.02*
|
64.44
|
11.93*
|
2.10
|
10.26*
|
532280.00***
|
Genotype × location
|
99
|
161.00
|
124.30
|
15.13*
|
71.32*
|
11.24*
|
1.06
|
8.15
|
233499.00
|
Residual
|
180
|
148.00
|
107.20
|
10.66
|
50.41
|
8.66
|
1.72
|
7.07
|
207464.00
|
Total
|
399
|
177.60
|
168.40
|
14.08
|
65.69
|
10.41
|
1.80
|
8.38
|
334119.00
|
Note: *, **,*** = Significance at 10%, 5% and 1%, respectively; ns = not significant; DF: degrees of freedom; DTF: days to flowering; DTM: days to maturity; PDL: pod length (cm), NPP: number of pods per plant; NSP: number of seeds per pod, SDS: seed size; HSW: hundred seed weight (g) and GYD: grain yield in kg per hectare
Table 3. Mean values for grain yield and yield components of 100 cowpea genotypes showing the top 10 and bottom 5 ranked genotypes based on grain yield (kg/ha) when assessed in two locations in Zambia
Genotype
|
DTF
|
DTM
|
PDL
|
NPP
|
NSP
|
SDS
|
HSW
|
GYD
|
Top 10 genotypes
|
CP411
|
34.50
|
73.75
|
20.15
|
32.25
|
16.50
|
3.00
|
13.48
|
2197.70
|
Chimponongo
|
51.50
|
79.50
|
19.52
|
26.75
|
16.75
|
5.00
|
20.95
|
2093.20
|
CP645
|
51.00
|
73.25
|
20.68
|
28.00
|
17.25
|
4.50
|
13.48
|
1899.30
|
MS1-8-1-4
|
39.75
|
68.50
|
21.20
|
33.25
|
15.50
|
5.00
|
15.03
|
1779.80
|
CP732
|
34.75
|
81.00
|
17.02
|
22.25
|
16.00
|
4.50
|
15.50
|
1672.40
|
BB14-16-2-2
|
36.75
|
74.00
|
19.70
|
25.25
|
15.50
|
3.00
|
11.25
|
1501.90
|
ZM3003
|
39.00
|
74.50
|
16.68
|
18.50
|
13.50
|
6.00
|
14.08
|
1454.10
|
CP421
|
44.75
|
72.75
|
19.90
|
24.00
|
18.25
|
3.00
|
16.23
|
1328.20
|
CP2
|
39.50
|
75.00
|
17.53
|
26.75
|
16.25
|
4.50
|
11.75
|
1252.70
|
CP601
|
40.00
|
73.50
|
17.85
|
22.25
|
16.75
|
5.50
|
13.83
|
1237.80
|
Bottom 5 genotypes
|
ZM2966
|
38.50
|
74.50
|
17.25
|
18.75
|
13.75
|
4.00
|
13.43
|
227.10
|
CP2231
|
45.75
|
77.00
|
15.41
|
16.75
|
12.75
|
6.00
|
15.13
|
225.40
|
ZM2954
|
47.00
|
73.75
|
15.90
|
19.25
|
13.50
|
5.50
|
14.68
|
188.20
|
CP1769
|
35.25
|
73.00
|
18.63
|
21.25
|
17.25
|
5.00
|
13.55
|
126.00
|
ZM6680
|
29.25
|
62.75
|
12.30
|
16.50
|
11.25
|
5.00
|
15.55
|
87.00
|
Mean
|
41.10
|
73.86
|
17.98
|
21.40
|
15.60
|
4.20
|
12.93
|
748.56
|
Minimum
|
14.00
|
31.00
|
6.00
|
3.00
|
0.00
|
3.00
|
9.10
|
32.55
|
Maximum
|
80.00
|
96.00
|
27.20
|
56.00
|
24.00
|
7.00
|
28.50
|
5471.24
|
SE
|
8.60
|
7.32
|
2.31
|
5.02
|
2.08
|
0.92
|
1.88
|
322.10
|
LSD (5%)
|
16.97
|
14.50
|
4.56
|
9.90
|
4.11
|
1.83
|
3.71
|
635.50
|
CV (%)
|
29.60
|
14.02
|
18.16
|
33.18
|
18.86
|
31.09
|
20.55
|
60.85
|
Note: CV: coefficient of variation; LSD: least significant difference; SE: standard error; DTF: days to flowering; DTM: days to maturity; PDL: pod length (UNIT?); NPP: number of pods per plant; NSP: number of seeds per pod; SDS: seed size (mm); HSW: hundred seed weight (g/100 seed); GYD: grain yield in kg ha-1
Table 4. Estimates of variance components and genetic parameters for yield and yield components among 100 cowpea genotypes evaluated in two locations in Zambia
Component
|
DTF
|
DTM
|
PDL
|
NPP
|
NSP
|
SDS
|
HSW
|
GYD
|
Genotype (G)
|
21.75
|
9.27
|
0.00
|
0.00
|
0.42
|
0.38
|
0.57
|
0.10
|
Location (L)
|
148.31
|
125.56
|
11.10
|
50.46
|
8.65
|
1.78
|
7.48
|
0.23
|
G x L
|
6.32
|
0.00
|
2.01
|
10.43
|
1.30
|
0.00
|
0.34
|
0.00
|
Total (G + L + G x L)
|
176.38
|
134.83
|
13.12
|
60.89
|
10.37
|
2.17
|
8.39
|
0.34
|
Phenotypic variance
|
61.99
|
40.66
|
3.78
|
17.83
|
3.23
|
0.83
|
2.61
|
0.16
|
Heritability (%)
|
35.00
|
23.00
|
0.00
|
0.00
|
13.00
|
46.00
|
22.00
|
64.00
|
GCV (%)
|
11.35
|
4.12
|
0.00
|
0.00
|
4.14
|
14.68
|
5.82
|
0.04
|
PCV (%)
|
19.16
|
8.63
|
10.82
|
19.73
|
11.52
|
21.58
|
12.48
|
0.05
|
GA
|
5.69
|
2.99
|
0.00
|
0.00
|
0.48
|
0.87
|
0.72
|
0.53
|
GA (%)
|
13.85
|
4.05
|
0.00
|
0.00
|
3.07
|
20.58
|
5.60
|
0.07
|
GCV: genotypic coefficient of variation; PCV: phenotypic coefficient of variation; GA: genetic advance; GA (%): genetic advance as a percentage of the mean: DTF: days to flowering; DTM: days to maturity; PDL: pod length; NPP: number of pods per plant; NSP: number of seeds per pod; SDS: Seed Size; HSW: hundred seed weight (g); GYD: grain yield in kg per hectare
Table 5. Correlation coefficients of grain yield and yield components among 100 cowpea genotypes evaluated at two locations in Zambia
Traits
|
DTF
|
DTM
|
PDL
|
NPP
|
NSP
|
SDS
|
HSWT
|
GYD
|
DTF
|
1
|
|
|
|
|
|
|
|
DTM
|
0.66**
|
1
|
|
|
|
|
|
|
PDL
|
-0.05
|
0.01
|
1
|
|
|
|
|
|
NPP
|
-0.05
|
-0.05
|
0.43**
|
1
|
|
|
|
|
NSP
|
-0.05
|
0.03
|
0.64**
|
0.38**
|
1
|
|
|
|
SDS
|
-0.01
|
0.00
|
-0.04
|
-0.09
|
-0.30**
|
1
|
|
|
HSW
|
0.01
|
-0.06
|
0.07
|
-0.09
|
-0.12
|
0.51***
|
1
|
|
GYD
|
-0.05
|
-0.07
|
0.42**
|
0.50**
|
0.46**
|
-0.12
|
0.04
|
1
|
Note: **.*** = Significant at 5% and 1% respectively; DTF: days to flowering; DTM: days to maturity; PDL: pod length (cm), NPP: number of pods per plant; NSP: number of seeds per pod, HSW: hundred seed weight (g), GYD: grain yield in kg per hectare
Table 6. Eigen values, variances and loading scores of eight quantitative traits among 100 cowpea genotypes assessed in two locations in Zambia
Traits
|
PC1
|
PC2
|
PC3
|
Eigen-values
|
2.52
|
1.68
|
1.50
|
Proportion variance (%)
|
31.49
|
20.97
|
18.78
|
Cumulative variance (%)
|
31.49
|
52.46
|
71.25
|
DTF
|
-0.09
|
0.88
|
-0.22
|
DTM
|
-0.03
|
0.87
|
-0.27
|
PDL
|
0.84
|
0.06
|
0.04
|
NPP
|
0.72
|
0.02
|
0.13
|
NSP
|
0.82
|
-0.01
|
-0.21
|
SDS
|
-0.25
|
0.18
|
0.78
|
HSW
|
0.02
|
0.31
|
0.80
|
GYD
|
0.75
|
0.11
|
0.27
|
DTF: days to flowering; DTM: days to maturity; PDL: pod length (cm), NPP: number of pods per plant; NSP: number of seeds per pod, HSW: hundred seed weight (g), GYD: grain yield in kg per hectare PC=principal component
Table 7. Genetic parameters of 90 cowpea germplasm collections assessed based on 14,116 SNP markers
Biological type
|
GD
|
PIC
|
MAF
|
Ho
|
F
|
Whole population
|
0.22
|
0.17
|
0.18
|
0.30
|
-0.35
|
Elite lines
|
0.21
|
0.17
|
0.19
|
0.30
|
-0.37
|
Landraces
|
0.22
|
0.18
|
0.22
|
0.23
|
-0.34
|
Mutant lines
|
0.26
|
0.21
|
0.18
|
0.35
|
-0.35
|
Range
|
0-0.5
|
0-0.38
|
0-0.5
|
0.25-0.36
|
-0.52 - -0.13
|
GD, genetic diversity; PIC, polymorphic information content; MAF, minor allele frequency, Ho, observed heterozygosity; F, inbreeding coefficient
Table 8. Analysis of molecular variance involving 90 cowpea accession based on source of collection
Source
|
Df
|
SS
|
MS
|
Estimated Variance.
|
Proportion of variance
|
Among Populations
|
2
|
45.57
|
22.78
|
0.54
|
8%
|
Within Populations
|
82
|
537.96
|
6.56
|
6.40
|
92%
|
Total
|
84
|
583.53
|
|
6.95
|
|
Df=degrees of freedom, SS=sum of squares, MS=mean squares
Table 9. Genetic differentiation (Fst) and inbreeding coefficients (Fis) among elite lines, landraces and mutant lines of cowpea evaluated in this study
Populations
|
Inbreeding coefficient (Fst)
|
|
G1
|
G2
|
G3
|
G1
|
-
|
0.006
|
0.012
|
G2
|
-0.364
|
-
|
-0.004
|
G3
|
-0.374
|
-0.351
|
-
|
|
Genetic differentiation (Fis)
|
G1 includes all breeding elite lines, G2 is comprised of landraces collected from farmers in Zambia, G3 consists of mutant lines