Combining Ability, Heritability and Heterosis for Grain and Biomass Yield in Cowpea (Vigna unguiculata L. Walp) Hybrids Evaluated under Drought Stress

Abstract

Developing dual-purpose cowpea varieties that combine high grain and biomass yields is important for food and nutritional security in drought-prone environments. This study evaluated combining ability, heterosis, and heritability among six cowpea parental lines and 10 F₁ hybrids produced using a half-diallel mating design under drought-stress conditions. General combining ability (GCA), specific combining ability (SCA), broad-sense heritability, narrow-sense heritability, and heterosis were estimated to assess the relative contributions of additive and non-additive genetic effects. Significant GCA and SCA effects were observed for all measured traits. The GCA:SCA ratio ranged from 0.41 for grain yield to 4.63 for pod width, indicating a greater contribution of non-additive effects to grain yield and a stronger additive influence on pod width. Broad-sense heritability ranged from 0.90 to 0.99, whereas narrow-sense heritability ranged from 0.28 to 0.79, showing that the potential response to selection differed among traits. Heterosis for grain and biomass yields varied widely among hybrids and between trials. MA67 × NA60 showed consistently positive heterosis for both grain and biomass yields, while MA50 × MA67 also showed positive heterosis for both traits across the two trials. The findings indicate that parent selection and hybrid evaluation should be combined when breeding drought-tolerant, dual-purpose cowpea, with further testing required across seasons and locations.