Genotype-by-environment interaction for grain yield among novel cowpea (Vigna unguiculata L.) selections derived by gamma irradiation

This study determined the effects of genotype-by-environment (G × E) interaction and stability of yield among elite cowpea (Vigna unguiculata L.) selections derived by gamma irradiation. The study was conducted in Namibia at three selected sites: Bagani, Mannheim, and Omahenene, during 2014/2015 and 2015/2016. Thirty-four newly developed mutant genotypes and three local checks were evaluated using a randomized complete block design with three replications. Grain yield data were analyzed using the additive main effects and multiplicative interaction (AMMI) and the genotype main effect plus genotype-by-environment interaction (GGE) biplot methods. The AMMI and GGE biplot models explained 77.49% and 75.57% of total observed genotypic variation, respectively. Bagani and Omahenene were the environments best discriminating the test genotypes during 2014/2015 and 2015/2016, respectively. Four promising mutant genotypes: G9 (ShL3P74), G10 (ShR3P4), G12 (ShR9P5), and G4 (ShL2P4), showed wide adaptation and grain yields of 2.83, 2.06, 1.99, and 1.95 t ha− 1, respectively. The novel mutant lines are useful genetic resources for production or future cowpea breeding programs in Namibia or similar environments.