INTRODUCTION

Vegetable cowpea popularly known as Yard long bean (Vigna unguiculata var. sesquipedalis) is an important leguminous vegetable crop of South India. Vegetable cowpea is an important vegetable grown as intercrop in different cropping systems. (Khanpara et al., 2016). In Vegetable cowpea, among the different parts analyzed shells were rich in dietary fiber. Seeds were nutrient dense as compared to pods and shells, but more in antinutrients (Tiwari et al., 2019). In Goa, pole type cowpea with indeterminate growth habit producing long green fleshy pods are preferred and fetch premium price in the market through out the year. There are many varieties released in case of bush type of cowpea but the availability of improved varieties in pole type vegetable cowpea is rather scanty. Not much work has been carried out on the genetic improvement of pole type vegetable cowpea. There is wide variability found for different morphological and other traits in the local types cultivated in the state of Goa. Exploration of genetic variability in the available germplasm is a prerequisite for initiation of any successful breeding programme. In spite of its popularity and importance very little effort has been made to upgrade the genetic makeup of this crop. Hence, the present investigation was carried out systematically to evaluate the local accessions to estimate the extent of genetic variability, heritability, genetic advance and genetic divergence in the locally collected germplasm of vegetable cowpea.

MATERIALS AND METHODS

Twenty nine genotypes of vegetable cowpea collected from different parts of Goa including three released varieties were evaluated in a randomized block design with two replications during rabi seasons starting from 2012-2016 in paddy fallow land. The soil is sandy loam with a pH of 5.1 with medium phosphorous and potassium availability. Recommended package of practices were followed to raise a good crop (Anon. 2004). Observations were recorded on twelve important quantitative characters, viz., plant height (cm), number of primary branches, leaf length (cm), leaf width (cm), days to first flowering, days to first harvest, pod length (cm), pod weight (g), pods per plant, number of seeds per pod, 100 seeds weight (g) and pod yield per plant on five randomly selected plants/genotype/replication. The analysis of variance was carried out as suggested by Panse and Sukhatme (1985). The genotypic and phenotypic coefficient of variation was calculated as per the formula suggested by Comstock and Robinson (1952). Heritability (broad sense) and genetic advance were worked out as per the procedure given by Burton and De Vane (1953) and Allard (1960).

RESULTS AND DISCUSSION

Among the twelve quantitative characters studied, the twenty nine vegetable cowpea genotypes exhibited highly significant differences for all the characters indicating high variability in the cowpea accessions (Table 1). Wide range of variation was observed for all the characters studied. Highest variation was observed for pod yield/plant, number of pods/plant and pod length (Table 2). Such a high variability for the above characters was also reported earlier by De Mooy (1985), Resmi (1998) and Narayanankutty et al. (2003).

In the present study, all the characters exhibited narrow differences between the value of PCV and GCV. This indicated low impact of environment on the expression of all the quantitative characters. The same was reported earlier by Narayanankutty et al. (2005).

The GCV value was maximum for pod yield per plant (g) followed by pod weight (g) and number of pods per plant. Low values of GCV were observed for days to first flowering, days to first harvest and number of seeds per pod (Table 2). Shobha and Vahab (1998) and Narayanankutty et al., (2003) reported high GCV for yield per plant and pod weight in vegetable cowpea. Low GCV values for days to first flowering and number of seeds per pod has been reported by Sreekumar et al., (1996). The results of analysis of variance for different traits are given in Table 3.

The high variability for pod yield per plant is apparent as the pod yield ranged from 315.25 to 2070.45 g / plant with an average of 827.48 g per plant. Pod yield depends on number of pods per plant, pod length and pod weight. Number of pods per plant ranged from 36.65 to 147.80. Pod weight depends on pod length, number of seeds per pod and hundred seeds weight. Wide variation was observed for all these characters in the present study. Similar findings have been reported by other workers (De Mooy(1985), Resmi (1998), Shobha and Vahab(1998) and Narayanankutty et al.,(2005)

With the help of variability and subsequent GCV alone, it is not possible to determine the amount of genetic variation that is heritable to the further generations. Burton and De Vane (1953) suggested that GCV combined with estimates of heritability would give the best results of genetic advance to be expected from selection. In the present study, heritability values were high (>90%) for all the characters studied except number of seeds per pod. High values of heritability for quantitative characters have also been reported by earlier workers, Sobha and Vahab (1998) and Narayanankutty et al. (2003). The accurate value for heritable variation can be estimated when heritability is combined with genetic advance. In the present study, high heritability coupled with high genetic advance was observed for pod yield per plant (g) and pod weight (g). This may be due to the preponderance of additive gene action for these characters there by indicating the advantages of selection for their improvement. High heritability coupled with highgenetic advance for above characters in vegetable cowpea has been reported by Resmi (1998) and Narayanankutty et al. (2003). Other characters viz.,days to first flowering, days to first harvest, numberof seeds per pod and leaf length has recorded highheritability of more than 90 per cent but their geneticadvance is very low (<30%) indicating the nonadditive gene action for these traits. This impliesimprovement of above traits by pyramiding desirablegenes through suitable hybridization programmes.

Table 1
Mean performance of vegetable cowpea germplasm of Goa

S.No.	Accessionnumber	Plantheight	No of 1obranches	Leaf l ength	Leaf width	Days to 1stflowering	Days to 1stharvest	Podl ength	Pod we ig ht	Pods perplant	No ofseeds per pod	100seeds we ig ht	Pod yield perplant
1	VCG1	4.49	6.60	13.48	9.68	43.00	57.60	35.17	10.58	77.00	14.61	17.32	820.50
2	VCG2	5.29	8.25	11.39	8.25	50.40	71.15	40.77	12.36	77.65	14.70	27.23	950.50
3	VCG3	4.85	5.25	10.63	7.77	51.30	71.00	47.35	13.90	74.40	13.76	25.65	1030.45
4	VCG4	6.29	4.10	12.54	9.56	46.40	60.00	64.70	35.52	58.35	13.19	19.22	2070.45
5	VCG5	3.46	5.60	9.98	6.47	52.20	69.70	40.85	9.26	54.50	17.34	25.25	505.50
6	VCG6	4.37	5.85	11.29	8.67	56.15	69.90	39.42	9.00	50.45	16.97	19.82	455.40
7	VCG7	3.90	5.25	11.13	9.33	48.50	62.90	37.53	8.47	67.15	15.15	14.90	565.65
8	VCG8	4.26	4.60	12.21	9.14	43.50	60.00	37.90	11.58	147.80	15.63	18.47	1710.65
9	VCG9	4.35	4.85	11.94	9.34	45.20	60.90	36.69	9.80	92.45	14.52	22.50	910.40
1 0	VCG10	4.41	6.65	10.84	7.97	50.60	66.90	40.32	11.13	72.50	14.77	13.45	810.00
1 1	VCG11	4.99	4.40	11.88	7.40	46.40	64.20	41.24	10.89	78.50	15.88	20.11	850.45
1 2	VCG12	4.64	4.80	11.08	7.27	51.90	77.10	43.01	9.60	58.40	16.55	15.39	555.40
1 3	VCG13	3.72	5.05	11.78	8.29	54.50	74.30	40.55	12.84	51.50	17.91	20.31	660.25
1 4	VCG14	4.31	4.15	13.73	9.93	44.20	61.20	41.19	9.74	65.05	15.51	20.51	635.25
1 5	VCG15	4.38	5.00	12.78	10.66	43.60	60.00	39.02	10.68	85.35	15.97	19.29	910.45
1 6	VCG16	4.75	4.85	12.24	9.58	45.30	60.70	27.97	6.22	83.60	15.26	20.93	520.65
1 7	VCG17	4.08	4.70	13.00	9.80	51.60	62.80	31.54	10.61	59.10	15.99	22.33	625.20
1 8	VCG18	4.46	4.25	13.60	9.93	55.20	67.00	33.36	8.66	36.65	16.11	20.11	315.25
1 9	VCG19	3.39	5.05	10.54	10.39	42.10	66.00	46.13	12.08	44.15	15.75	15.04	527.30
2 0	VCG20	4.64	4.85	11.42	9.05	44.40	71.90	51.95	12.03	52.20	14.97	17.55	606.20
2 1	VCG21	4.43	5.55	11.89	9.24	44.00	71.60	48.14	11.13	86.45	13.03	20.05	908.45
2 2	VCG22	4.95	6.25	12.07	10.21	46.10	70.20	59.50	19.13	72.50	16.86	22.29	1374.15
2 3	VCG23	4.10	6.15	11.74	9.87	44.00	65.60	55.64	10.57	105.50	16.04	20.39	1183.55
2 4	VCG24	4.72	5.30	11.14	9.61	51.80	78.40	46.87	13.31	91.60	13.06	23.56	1262.45
2 5	VCG25	4.86	4.95	12.33	9.10	51.00	77.60	48.77	14.09	48.80	13.61	20.61	697.50
2 6	VCG26	3.95	4.65	13.13	11.20	48.70	62.50	51.01	13.94	64.10	13.61	19.84	783.10
2 7	Vijayanthi	2.90	6.15	11.13	10.95	50.70	72.00	47.23	10.75	50.70	12.94	23.21	408.60
2 8	A Garima	1.00	5.20	10.00	10.89	42.90	64.60	51.40	10.95	71.30	12.20	21.96	707.80
2 9	A Suman	1.05	5.10	9.39	10.09	45.90	65.00	54.28	12.07	65.20	13.05	19.94	635.45
	CD(0.05)	0.61	6.60	0.82	0.71	3.06	3.98	3.36	1.63	7.36	1.92	1.62	123.72

Table 2
Range, mean, PCV, GCV, heritability and genetic advance for twelve quantitative characters in vegetable cowpea

Characters	Mean ± SEm	Range	Phenotypic variance	Genotypic variance	PCV	GCV	Heritability (%)	Genetic advance (%)
Plant height	4.170±0.210	1.00 - 6.29	2.31	2.22	36.45	35.74	96.19	72.21
No of 1o branches	5.29±0.24	4.10 - 8.25	1.59	1.47	23.81	22.95	92.92	45.58
Leaf length	11.73±0.29	9.39 - 13.73	2.41	2.25	13.24	12.79	93.28	25.44
Leaf width	9.29±0.25	6.46 - 11.19	2.69	2.57	17.64	17.25	95.55	34.73
Days to 1st flowering	47.98±1.06	42.10 - 56.15	33.88	31.64	12.13	11.72	93.40	23.34
Days to 1st harvest	66.99±1.38	57.60 - 78.40	67.72	63.95	12.28	11.94	94.43	23.89
Pod length	44.12±1.16	27.97 - 64.69	142.48	139.79	27.06	26.80	98.12	54.69
Pod weight	12.09±0.56	6.22 - 35.52	51.48	50.85	59.31	58.94	98.77	120.67
No of pods/plant	70.45±2.54	36.65 - 147.80	967.57	954.66	44.17	43.86	98.67	89.75
No of seeds/pod	14.99±0.66	12.20 - 17.91	4.48	3.60	14.11	12.66	80.43	23.38
100 seed weight	20.25±0.56	13.45 - 27.23	20.50	19.88	22.36	22.02	96.96	44.67
Yield per plant	827.48±42.72	315.25 - 2070.45	303498.45	299849.38	66.58	66.18	98.79	135.49

Table 3
Analysis of Variance for Different traits in Vegetable Cowpea germplasm of Goa

* Significant at 1% level

Sources of Variation	d.f.	Mean Sun of Squares
		Plant height	No of branches	Leaf length	Leaf width	Days to 1stflowering	Days to 1stharvest	Pod length	Pod weight	Pods per plant	No of seeds per pod	100seeds weight	Pod yield perplant
Treatments	28.00	64.67*	44.42	67.53	75.31	948.59*	1896.24	3989.55*	1441.39*	27091.81	125.41	97956.69	574.08*
Replications	1.00	0.47	0.08	0.07	0.05	0.03	0.38	1.32	0.65	0.02	1.07	1383.77	0.21
Residual	28.00	2.47	3.15	4.54	3.35	62.58	105.70	75.19	17.72	361.41	24.55	2174.08	17.48

Table 4
Clustering pattern of vegetable cowpea genotypes

* Significant at 1% level

Cluster No.	Number of genotypes	Constituent genotypes
I	5	VCG1, VCG2, VCG3, VCG9, VCG15
II	2	A Suman , A Garima
III	2	VCG6, VCG13
IV	2	VCG18, VCG17
V	2	VCG11, VCG14
VI	2	VCG25, VCG20
VII	2	VCG10, VCG12
VIII	2	VCG7, VCG19
IX	2	VCG24, VCG21
X	2	Vijayanthi, VCG26
XI	2	VCG23, VCG22
XII	2	VCG5, VCG16
XIII	1	VCG4
XIV	1	VCG8

Table 5
Phenotypic correlation coefficient among different quantitative characters in vegetable cowpea

* Significant at 5 % level ** Significant at 1 % level

The success of any hybridization programme depends on the genetic diversity present in the parents. In the present study, the twenty nine genotypes could be grouped in to fourteen clusters based on genetic distance (Table 4). The cluster I was the largest comprising of five genotypes and remaining clusters had two genotypes each except thirteen and fourteen that had one genotype each.

The clustering pattern in the present study did not follow any uniform pattern. The clustering pattern was irregular and the same type of distribution was earlier reported by Patil and Bhapkar (1987) and Narayanankutty et al. (2005).

The correlation studies provide reliable information on the nature and extent of relationship for bringing about improvement in yield and other traits. The estimates of correlation coefficients is presented in Table 5. Characters showing positive and highly significant correlation with yield per plant were pod weight (0.737) and number of pods per plant (0.596). On the other hand, yield had negative and significant correlation with days to first flowering (-0.318) and number of seeds per pod (-0.203). This is in accordance with the results of Narayanankutty et al. (2005).

In the present study, high coefficient of variation was observed for pod yield per plant, pod weight, number of pods per plant and pod length indicating their significant contribution in determining the inter cluster distances. Hence, selection of parents differing in traits such as pod weight, pod yield per plant , number of pods/plant and pod length will be more useful in future breeding programmes.

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