Genetic variation and genetic advance in cowpea based on yield and yield-related traits

Figures & data

Table 1. List of cowpea accessions used in the study.

Serial Number	Accession name	Origin/source	Serial Number	Accession name	Origin/source
1	RV 361	South Africa	51	RV 104	South Africa
2	RV 465	South Africa	52	RV 352	South Africa
3	RV 438	South Africa	53	RV 113	South Africa
4	RV 202	South Africa	54	RV 471	South Africa
5	TVU 9596	IITA	55	RV 207	South Africa
6	RV 551	South Africa	56	RV 440	South Africa
7	98D-1399	IITA	57	RV 43	South Africa
8	RV 568	South Africa	58	RV 173	South Africa
9	RV 499	South Africa	59	RV 501	South Africa
10	RV 343	South Africa	60	RV 320	South Africa
11	RV 553	South Africa	61	RV 555	South Africa
12	TVU 14190	IITA	62	RV 84	South Africa
13	RV 470	South Africa	63	RV 342	South Africa
14	98K-503-1	IITA	64	90K-284-2	IITA
15	RV 416	South Africa	65	TVU 3416	IITA
16	83s-911	IITA	66	RV 504	South Africa
17	RV 121	South Africa	67	95K-589-2	IITA
18	RV 16	South Africa	68	RV 204	South Africa
19	RV 487	South Africa	69	RV 28	South Africa
20	RV 558	South Africa	70	RV 351	South Africa
21	RV 382	South Africa	71	RV 441	South Africa
22	RV 157	South Africa	72	RV 500	South Africa
23	RV 329	South Africa	73	ITOOK-1263	IITA
24	RV 457	South Africa	74	RV 446	South Africa
25	97K-499-35	IITA	75	RV 189	South Africa
26	99K-494-6	IITA	76	Dr. Saunders	South Africa
27	RV 419	South Africa	77	RV 403	South Africa
28	CH-47	IITA	78	RV 498	South Africa
29	RV 503	South Africa	79	TVU 12746	IITA
30	RV 10	South Africa	80	PAN 311	South Africa
31	RV 315	South Africa	81	GLENDA	South Africa
32	RV 439	South Africa	82	RV 550	South Africa
33	RV 502	South Africa	83	TVU 12637	IITA
34	RV 409	South Africa	84	RV 443	South Africa
35	Bechuana White	South Africa	85	TVU 9443	IITA
36	RV 341	South Africa	86	RV 554	South Africa
37	RV 497	South Africa	87	RV 411	South Africa
38	RV 344	South Africa	88	RV 161	South Africa
39	RV 414	South Africa	89	RV 321	South Africa
40	RV 111	South Africa	90	RV 115	South Africa
41	RV 386	South Africa	91	RV 213	South Africa
42	RV 505	South Africa	92	RV 417	South Africa
43	TVU 9620	IITA	93	RV 477	South Africa
44	TVU 2095	IITA	94	86D-1010	IITA
45	RV 464	South Africa	95	TVU 13998	IITA
46	RV 353	South Africa	96	RV 194	South Africa
47	RV 205	South Africa	97	TVU 13778	IITA
48	RV 442	South Africa	98	TVU 11986	IITA
49	98K-476-8	IITA	99	RV 165	South Africa
50	RV 574	South Africa	100	RV 126	South Africa

Note: IITA, International Institute of Tropical Agriculture.

Table 2. Analysis of variance showing mean square values and significance test of agronomic traits among cowpea genotypes in different sites during 2017/18 season.

Source of variation	df	DFW	BRN	PNP	PWP	HSW	SPD	SNP	GRY
Genotype (G)	97	383.3*	75.68***	855.5***	1066.9***	63.55***	14.289***	26415***	865.1***
Location (L)	1	320,429.4***	37,825.89***	65,675.6***	123,967.1***	747.27***	0.000*	22,982ns	7397.1***
G x L	90	223.3ns	87.85***	614.0***	732.4ns	20.88ns	1.62ns	14,564ns	617.4ns
Residual	271	243.4	33.24	771.1	666.5	20.64	8.302	17,162	601.5

Notes: HSW, hundred seed weight; BRN, number of branches; DTF, days to flowering; PNP, pod number per plant; PWP, pod weight per plant; SPD, seed number per pod; SNP, seed number per plant; GY, grain yield; df, degrees of freedom; ** p < 0.01; *** p < 0.001; ns, non-significant.

Figure 1. Correlation coefficient matrix showing associations of agronomic traits among cowpea genotypes evaluated across two environments. DTF, days to flowering; BRN, number of branches; PNP, pod number per plant; PWP, pod weight per plant; HSW, hundred seed weight; SPD, seed number per pod; SNP, seed number per plant; GY, grain yield.

Table 3. Direct (diagonal and bold font) and indirect (off-diagonal) path coefficient values of agronomic traits in cowpea.

Traits	DFW	BRN	PNP	PWP	SPD	HSW	SNP	GRYrg
DFW	0 . 03	−0.11	0.00	0.19	0.00	0.00	0.03	0.14ns
BRN	−0.01	0.42	0.00	−0.14	0.00	0.02	0.02	0.30**
PNP	0.00	0.19	−0.01	0.39	0.00	0.01	0.13	0.71**
PWP	0.01	−0.09	−0.01	0.71	0.00	0.02	0.11	0.76**
SPD	0.00	0.01	0.00	0.24	−0.01	0.01	0.06	0.30**
HSW	0.00	0.08	0.00	0.17	0.00	0.08	0.00	0.33**
SNP	0.01	0.05	−0.01	0.54	0.00	0.00	0.15	0.73**

Notes: Days to flowering; BRN, number of branches; PNP, pod number per plant; PWP, pod weight per plant; SPD, seed number per pod; HSW, hundred seed weight; SNP, seed number per plant; GRYrg = genotypic correlation with grain yield,** significant at P <0.001 significance level; ns, non-significant.

Table 4. Principal component analysis showing eigenvectors, percent and cumulative variation of agronomic traits among 100 cowpea genotypes.

	Principal components
Traits	PC1	PC2	PC3
HSW	0.21	−0.66	0.01
BRN	0.24	0.87	0.13
DFW	0.89	0.25	0.07
PNP	0.78	−0.43	0.28
PWP	0.52	−0.06	−0.04
SPD	0.05	0.08	0.97
SNP	0.95	−0.07	−0.09
GRY	0.84	0.04	0.36
Eigenvectors	3.5	1.5	1.0
Percentage variation (%)	43.8	18.6	12.7
Cumulative variation (%)	43.8	62.5	75.2

Notes: HSW, hundred seed weight; BRN, number of branches; DTF, days to flowering; PNP, pod number per plant; PWP, pod weight per plant; SPD, seed number per pod; SNP, seed number per plant; GY, grain yield.

Figure 2. Bi-plots of principal components showing % variation accounted for PC1 vs. PC2, PC1 vs. PC3 and PC2 vs. PC3 and relationships among cowpea genotypes and agronomic traits based on combined data across test environments. DFW, days to flowering; BRN, number of branches; PNP, pod number per plant; PWP, pod weight per plant; SPD, seed number per pod; HSW, hundred seed weight; SNP, seed number per plant; GRY, grain yield.

Table 5. Estimates of mean, variance, broad sense heritability, genotypic and phenotypic coefficients of variation and genetic advance of agronomic traits in cowpea.

Trait	Mean ± SE	MSG	MSE	MSgl	δ^2gl	δ^2g	δ^2p	δ^2e	PCV	GCV	H^2	GA	GG%
DFW	48.41 ± 10.58	383.30	246.40	223.30	100.10	160.00	381.60	246.40	28.08	26.13	91.93	260.57	538.29
BRN	11.71 ± 4.003	87.85	33.24	75.68	59.06	12.17	32.65	33.24	16.70	29.79	67.27	71.86	613.72
PNP	35.19 ± 14.21	855.50	398.00	614.00	415.00	241.50	582.50	398.00	40.69	44.16	91.46	320.13	909.79
PWP	29.06 ± 19.09	1066.90	666.50	732.40	399.15	334.50	835.63	666.50	53.62	62.93	80.03	376.76	1296.42
HSW	10.89 ± 2.73	63.55	20.64	20.88	10.56	42.67	90.50	20.64	28.82	59.97	97.15	134.56	1235.31
SPD	15.65 ± 3.257	14.29	8.30	1.62	−2.53	12.67	27.41	8.30	13.23	22.74	96.21	173.31	468.40
SNP	199.14 ± 83.02	26415.00	13549.00	14564.00	7789.50	11851.00	27089.25	13549.00	116.63	54.67	93.75	2242.56	1126.11
GRY	33.58 ± 17.49	865.10	601. 50	617.40	316.65	247.70	645.78	601.50	43.85	46.87	38.36	324.21	965.56

Notes: DFW, days to flowering; BRN, number of branches; PNP, pod number per plant; PWP, pod weight per plant; SPD, seed number per pod; HSW, hundred seed weight; SNP, seed number per plant; GRY, with grain yield; MSG, Mean square genotype; MSE, mean square error; MSgl, mean square genotype x location; δ²gl, Genotype x location variance; δ²g, genotypic variance; δ²p, phenotypic variance; δ²e, environmental variance; PCV, phenotypic coefficient of variance; GCV, genotypic coefficient of variance; H², heritability; GA, genetic advance; GG%, percent of genetic mean.