Digenic Interactions on Yield in Yardlong Bean: A Generation Mean Analysis

Vegetable cowpea [Vigna unguiculata ssp. sesquipedalis (L.) Verdc.] is a distinct form of cowpea cultivated in southern Asia and the Far East for its immature pods. Six parameter generation mean analysis of three cowpea crosses revealed complex gene action for several yield-related traits. Significant scale tests and epistasis indicated the inadequacy of the simple additive-dominance model, underscoring the role of non-allelic interactions in trait inheritance. Additive × additive, additive × dominance, and dominance × dominance effects were observed for traits such as pod length, pod yield per plant, pods per plant, and root weight. The presence of duplicate and complementary epistasis suggests that hybridization followed by selection in segregating generations would be effective for improving these traits. Traits like pod breadth, seeds per pod, and 100-seed weight, which lacked significant epistasis, can be improved using additive-dominance models. Recombination breeding is recommended for enhancing pod yield and pod weight.