Genetic variability and trait association in cowpea (Vigna unguiculata L.) genotypes for yield and reproductive efficiency

Abstract

Cowpea (Vigna unguiculata L. Walp.) is a vital food legume cultivated widely in tropical and subtropical regions for its protein-rich seeds, fodder value, and ability to thrive in marginal environments. The present investigation was conducted to assess genetic variability, estimate heritability and genetic advance, and determine trait associations related to yield and reproductive efficiency in 22 diverse cowpea genotypes. Significant differences were observed among genotypes for all 13 traits studied, indicating substantial genetic variation. High genotypic and phenotypic coefficients of variation were recorded for seed yield per plant (GCV: 34.77%, PCV: 36.13%), secondary branches per plant (GCV: 39.00%, PCV: 40.04%), and plant height (GCV: 32.48%, PCV: 33.32%). Broad-sense heritability estimates were high for days to 50% flowering (95.17%), seed yield per plant (92.57%), and number of pods per plant (90.81%), coupled with high genetic advance, suggesting additive gene action. Genotypic correlation analysis revealed strong positive associations of seed yield per plant with number of primary branches (r = 0.988), secondary branches (r = 0.837), pods per plant (r = 0.895), and plant height (r = 0.667). Pollen viability and germination also showed moderate associations with yield, highlighting their relevance for reproductive success. These results emphasize the importance of integrating both agronomic and reproductive traits for selection. The identified high-heritability, high-correlation traits provide a strong basis for improving seed yield and reproductive efficiency in cowpea through targeted breeding strategies.