Genetic and Environmental Effects on Nodulation and Yield Among Selected Cowpea (<i>Vigna unguiculata</i> [L.] Walp) Genotypes in Uganda

Abstract

Cowpea ( Vigna unguiculata [L.] Walp) is among the most important legume crops grown especially in the Eastern and Northern regions of Uganda. It is a climate‐resilient and protein‐rich legume crop that also serves as a soil fertility restorer. This crop is a mainstay across Africa, Southeast Asia, and certain areas in America. Nevertheless, the productivity of the Ugandan‐cultivated cowpea varieties remains relatively low compared to improved cultivars when subjected to optimal field management. The objective of this study was to evaluate the performance of selected cowpea genotypes with a specific focus on analyzing the effect of the interaction between genotype and environment on nodulation capacity and yield performance in Uganda field conditions. The research evaluated 35 cowpea genotypes using a 5 × 7 alpha lattice design, with three replicates across seven test environments in Uganda. The additive main effect and multiplicative interaction (AMMI) for the number of nodules (NN) per plant and seed yield per plot showed significant differences for genotypes, environments, and genotype‐by‐environment interaction. However, the environmental effect was the largest contributor to the total variation in NN and seed yield compared with genetic and G × E interactions. MUARIK 2023A was the most favorable environment while Ngetta (Lira23B) was the most unfavorable for all the studied traits. Kitgum 2023A was the most discriminant environment for NN and seed yield. Across environments, genotypes UCR_5280 (G43) and TVu‐13958 (G2) were more stable for nodulation ability while TVu‐6439 (G23) and CB3 (G6) were the most stable for seed yield. Overall, genotypes TVu‐14691 (G13) and TVu‐1477 (G27) combined relative performance for the two studied traits. The findings of this study show the potential of using the current genetic material in breeding for high yield and nodulation capacity in cowpea through intensive selection and introgression. However, further evaluation of the cowpea germplasm in diverse growing regions would make selection more effective and accelerate genetic gains.