Phenotypic description of elite cowpea (Vigna ungiculata L. Walp) genotypes grown in drought-prone environments using agronomic traits

Identification and selection of cowpea genotypes possessing suitable agronomic attributes is key for cultivar development to increase production. The objective of this study was to evaluate cowpea genotypes using agronomic traits to aid selection and identification of best genotypes for adoption and breeding to develop high-yielding cultivars. Agronomic traits of 20 cowpea genotypes were evaluated under Tompi Seleka and Polokwane environments using a completely randomised block design. Significant (P ≤ 0.01) genotype effect was identified for agronomic traits, whereas environment effect was significant (P ≤ 0.05) for number of productive branches (NB), leaf width (LW), leaf length (LL), hundred-seed weight (HSW) and grain yield (GY). Significant genotype-by-environment interaction effect was observed for pod length (PL), pod width (PW) and number of seeds per pod (SPP). Correlation analysis revealed positive and significant associations between NB with LW (r = 0.58; P ≤ 0.01), LL (r = 0.67; P ≤ 0.01), number of pods per plant (PPP) (r = 0.56; P ≤ 0.01) and HSW (r = 0.47; P ≤ 0.05). LW was positively and significantly correlated with LL (r = 0.71; P ≤ 0.00), PPP (r = 0.56; P ≤ 0.01) and SPP (r = 0.58; P ≤ 0.01). Positive and significant correlation was observed between LL with chlorophyll content index (CCI) (r = 0.54; P ≤ 0.05), PPP (r = 0.68; P ≤ 0.01) and pod length (PL) (r = 0.52; P ≤ 0.05). PW was positively and significantly associated with PL (r = 0.68; P ≤ 0.01) and SPP (r = 0.61; P ≤ 0.01), whereas PL was positively associated with SPP (r = 0.82; P ≤ 0.01). Cowpea genotypes CH14, Embo buff, IT89D-349, IT96D-602, Veg cowpea 1, Veg cowpea 2, Veg cowpea 3 and Veg cowpea dakama red recorded high NB, plant height (PH), LL, LW, chlorophyll content index (CCI), number of pods per plant (PPP), HSW and GY. Also, genotypes 2460, IT96D-748, Oukawa, Ukaluleni, Veg cowpea dakama cream and Vigna Onb were associated with PL, SPP and PW. The identified genotypes possessing suitable agronomic traits are recommended for farmer-adoption and inclusion in breeding programs for cultivar development.