Phenotypic diversity among cowpea mutants and accessions for grain yield and yield components

Phenotypic characterization of cowpea germplasm collections is an essential step for the cowpea genetic improvement. The objectives of the study were to determine the phenotypic diversity and characterize cowpea mutants and accessions for grain yield and yield components, to identify their superior mutants and accessions, and to determine the correlation between measured characteristics. Thirty-one cowpea genotypes (16 Namibian mutants, seven International Institute of Tropical Agriculture (IITA) genotypes and eight South Africa genotypes) were planted in five different environments in South Africa during the 2021/2022 cropping season. Trials were laid out in randomised complete block designs with replications and the data was collected for grain yield and agronomic traits. Significant (P <= 0.05) genotype, environment and genotype by environment interaction effects were observed for all grain yield and yield components. Moderate to high broad-sense heritability (H-2) (> 50%) was observed for all yield components. The grain yield (GY) was significant and positive correlated pod weight per pod (PWP), number of seeds per plant (NSPPx), number of pods per plant (NPP), harvest index (HI), and seed weight per plant (SWP) suggesting the possibility of simultaneous improvement of these traits. In the principal component analysis, Namibian mutant genotypes ShL2P7, ShR4P1, NKR1P3 and BrR11P2 were associated with high NSPPx, PWP and GY. The clustered heat map identified a group of Namibian mutants (NKR1P3, BrR11P2, ShL2P7, ShR2P11 and ShR10P12), IITA geno-type (98K-476-8) and South African genotypes (Glenda, Dr Saunders, Enchore, and Oloyin) which was associated with high GY, PWP, NSPPx, NPP, SWP and HI. The identified superior cowpea mutants for grain yield and yield components can be used to develop high yielding varieties.(c) 2023 The Authors. Published by Elsevier B.V. on behalf of South African Association of Botanists. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)