Heterotic response and inbreeding depression in seed traits and other related attributes of cowpea (Vigna unguiculata [L.] Walp.)

Abstract

Cowpea is a vital source of plant protein in West Africa, yet its productivity remains low due to the use of unimproved cultivars. To address this, breeding programs aim to develop improved varieties. This study, conducted in 2022 at the Teaching and Research Farms of the University of Cape Coast, evaluated heterosis and inbreeding depression in cowpea involving 13 crosses generated through North Carolina Design II. The results showed that hybrids from UCC15-36 × UCC15-07, UCC15-36 × IT93K-693-2, UCC15-36 × Aluba Kpole,  UCC15-25 × IT93K-693-2, UCC15-41 × Kubi, UCC15-03× Kubi and UCC15-41× Kubi expressed positive heterosis  for seed traits, including length, width, thickness, and 100-seed weight, indicating strong yield potential compared to their parental lines. The magnitude of the inbreeding depression was high in plant height, and number of branches. The observed performance was likely influenced by dominance, additive × additive, and other non-additive gene effects, suggesting that selection for these traits would be more effective in later generations. Thus, both additive and non-additive effects can be exploited to enhance cowpea improvement.