Estimates of pod length heritability and efficiency of selection at early generation as a tool for developing a new cowpea (Vigna unguiculata (L.) Walp) cultivars under drought stress

Ultimate aim of any breeder is to develop hybrid with high pod yield, particularly under stress environment. Selection for these traits in cowpea will be more appropriate in the early generation of hybridization under water stress. This study was conducted to determine pod length in association with ۱۰۰ seed weight, number of pods per plant and number of seeds per pod heritability and efficiency of selection under drought stress. Contrasting cowpea parents; IT۹۷k -۴۹۹-۳۵ and Tvu ۷۷۷۸ and F۱, RF۱ and F۲ generations were planted in a field condition under water stressed and non water stressed environments. The analysis of variance indicated significant differences among generations for characters measured under water stressed and non water stressed environments. Water stressed effect significantly reduced the mean values of number of pods per plant across the generations, number of seed per pod for the parental genotypes, but however had slight effect on pod length and ۱۰۰ seed weight across the generations. Pod length had highly genetic positive correlation coefficients with ۱۰۰ seed weight (۰.۷۱, ۰.۷۹) under non water stressed and water stressed, below average between the former (۰.۳۳) and number of pods per plant under non water stressed, number of seed per pod (۰.۵۷) under water stressed environment, but the association was completely broken down under water stressed environment. The estimates of broad sense heritability measured were relatively high for all the traits measured under both environments. Relative efficiency of indirect to direct were lower than ۱.۰ suggesting that, the predicted gain in pod length from selection applied to ۱۰۰ seed weight, number of pods per plant and number of seeds per pod was less than the predicted gain from direct selection. Significant and relatively large additive gene effect compared with non additive gene effect, hence effective selection at early generation of hybridization.Ultimate aim of any breeder is to develop hybrid with high pod yield, particularly under stress environment. Selection for these traits in cowpea will be more appropriate in the early generation of hybridization under water stress. This study was conducted to determine pod length in association with ۱۰۰ seed weight, number of pods per plant and number of seeds per pod heritability and efficiency of selection under drought stress. Contrasting cowpea parents; IT۹۷k -۴۹۹-۳۵ and Tvu ۷۷۷۸ and F۱, RF۱ and F۲ generations were planted in a field condition under water stressed and non water stressed environments. The analysis of variance indicated significant differences among generations for characters measured under water stressed and non water stressed environments. Water stressed effect significantly reduced the mean values of number of pods per plant across the generations, number of seed per pod for the parental genotypes, but however had slight effect on pod length and ۱۰۰ seed weight across the generations. Pod length had highly genetic positive correlation coefficients with ۱۰۰ seed weight (۰.۷۱, ۰.۷۹) under non water stressed and water stressed, below average between the former (۰.۳۳) and number of pods per plant under non water stressed, number of seed per pod (۰.۵۷) under water stressed environment, but the association was completely broken down under water stressed environment. The estimates of broad sense heritability measured were relatively high for all the traits measured under both environments. Relative efficiency of indirect to direct were lower than ۱.۰ suggesting that, the predicted gain in pod length from selection applied to ۱۰۰ seed weight, number of pods per plant and number of seeds per pod was less than the predicted gain from direct selection. Significant and relatively large additive gene effect compared with non additive gene effect, hence effective selection at early generation of hybridization.

Keywords:

Heritability , Efficiency of selection , Cowpea , Drought stress