Phenotypic Analysis of Seed Yield and Yield Components in Cowpea (Vigna unguiculata L., Walp)

Poor seed yield remains a great challenge for cowpea production in sub-Sahara Africa and continuous evaluation of available genetic resource to develop high and stable yielding varieties is the panacea to this regional food security conundrum. In this study, 21 cowpea breeding lines were evaluated for phenotypic analysis of seed yield components for two years in a randomized complete block design of 3 replications. All the yield components exhibited significant genotypic variation, while flowering, pod maturity and seed yield traits recorded significant variation for years and its interactions. These cowpeas, which are predominantly early-medium maturing biotypes, exhibited relative phenotypic stability for the yield components across years (seasons) except seed yield, being a final product of complex physiological process. Relationships between flowering/pod maturity and seed size were positive and significant. By contrast, pods/plant, seeds/plant and total seed yield recorded negative correlations with pod maturity. However, seeds/plant and pods/plant are the most contributory components to seed-yield with correlation coefficients of r=0.95, 0.89, respectively. Although seed size had negative correlation with seeds/pod, but strong linkage between seed number (seeds/pod, seeds/plant) and seed yield; and additive gene nature of seed size, suggest a weak size-number trade-off in cowpea. Genetic variance components indicates high genetic contributions over non-genetic to plant phenotypic variability with high heritability values (0.75-0.91). Six cowpea lines (IT10K-837-1, IT07K-299-6, IT10K-815-5, IT10K-817-7, IT08K-150-24, and IT11K-61-82) with multiple quality yield traits could be selected for immediate farmers use and future genetic improvement.