Variability and hetrosis in bush type vegetable cowpea (Vigna unguiculata(L) Walp.)

Abstract

etc. The present investigation on ‘variability and hetrosis in bush type vegetable cowpea (Vignaunguiculata (L.) walp.)’ was conducted at the College of Horticulture, Vellanikkara, Thrissur during 1992 - 94. Thirty one genotypes of cowpea collected from different parts of the country were grown in a randomised block design with three replications to assess the extent of genetic variability for fifteen characters viz. plant height, spread, primary branches, days to flowering, days to harvest, pod length, pod girth, pod weight, seeds/pod, flower bunches, pods/cluster, pods/kg, 100 seed weight, pods/plant, and yield/plant. The genotypic and phenotypic coefficients of variation, heritability, genetic advance and genetic gain were estimated. Based on D2 analysis and morphological observations, ten parents were selected and crossed in all possible combinations in a 10 x 10 diallel to produce 45 F1 hybrids. These F1 hybrids were evaluated along with their parents to derive information on general and specific combining ability effects and heterosis. Significant differences were observed among the 31 genotypes for all the fifteen characters studied. The highest genotypic coefficient of variation was observed for pods/kg, pod weight and yield. High heritability coupled with high genetic gain was observed for these traits. Days to harvest, pod length, pod girth, pod weight and yield. High heritability coupled with high genetic gain was observed for these traits. Days to harvest, pod length, pod girth, pod weight, pods/kg, seeds/pod and 100 seed weight were highly correlated with yield. Pod weight exerted the maximum direct effect on yield. Based on genetic divergence the 31 genotypes were grouped into six clusters. Polyacrylamide gel electrophoresis of cowpea seed proteins showed marked variation in banding pattern. Different cowpea varieties could be distinguished by the species specific bands. Significant gca and sca variances were observed for all the traits. Amb – 1, selection 263 and selection 2 - 1 were the best general combiners for earliness. Hybrids resulted from Amb – 1 x ArkaGarima and Vu – 18 x Amb – 1 recorded high sca effects for earliness. ArkaGarima and selection 2 – were the best general combiners for yield. The hybrids Vu 18 x ArkaGarima and Selection 2 – 1 x Vs 389 evinced high sca effects for yield. Significant heterosis were observed for all the traits in many hybrids. Several hybrids recorded significant negative relative heterosis, heterobeltiosis and standard heterosis for earliness. Amb – 1 x ArkaGarima and Vu – 18 x Amb – 1 were significantly early to flower compared to standard variety, ArkaGarima. Relative heterosis and heterobeltiosis were observed in many hybrids for yield/plant. Selection 2–1 x VS 389 and Vu – 18 x Amb – 1 showed high relative heterosis as well as heterobeltiosis. Vu – 18 x ArkaGarima and Selection 2 – 1 x VS 389 were the promising hybrids which exceeded the standard variety ArkaGarima for yield/plant.