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Cowpea [Vigna unguiculata (L.) Walp.] is a valuable crop for subsistence farmers in sub-Saharan Africa. Characterization and evaluation of cowpea germplasm collections based on seed yield for genotype × environment (GE) interactions can assist in improving the adaptability and stability across environments. The objectives of this study were to determine genetic variability in the germplasm collection, to determine the magnitude of GE interactions, to identify superior genotypes across environments, and to determine the phenotypic correlations among the seed yield and related traits. Seventy-five cowpea genotypes were planted in three different locations during the 2017-2018 and 2018-2019 cropping seasons, and data were collected for seed yield and its components. Highly significant (P < .001) genotype effect for seed yield traits suggested great genetic differences among the tested populations. Significant (P < .05) genotype × location interaction (GL), genotype × season interaction (GS), and genotype × location × season interaction (GLS) effects were observed for seed yield traits, indicating the presence of complex GE interactions. The GLS effect was more than the GL and GS effects for seed yield, 100-seed weight, number of pods, and pod width, highlighting the difficulty in genetic improvement of these traits. Cowpea genotypes 6 (ARC006), 49 (ARC049), 63 (IT90K-76), and 57 (PAN311) showed high yield, wide adaptation, and stability. Genotype 58 (NGOII) and 1 (ARC001) showed high yield, instability, and specific adaptation. No clear mega-environments were identified. Significant (P < .05) correlations were observed among most of the traits evaluated. The results obtained can serve as a guide and basis of germplasm management and improvement of cowpea seed yield.

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