Phenological Diversity and Yield-Component Variation among Early-Maturing Cowpea (Vigna unguiculata [L.] Walp.) Accessions in the Southern Guinea Savanna of Nigeria

Cowpea (Vigna unguiculata [L.] Walp.) is an important grain legume in sub-Saharan Africa. However, the value of improved germplasm depends on the fit between crop duration, reproductive architecture and the target production environment. This study evaluated 20 early-maturing cowpea accessions at the National Cereals Research Institute (NCRI), Badeggi, Niger State, Nigeria, using a randomised complete block design with three replications. Data were collected on branch number, flowering and maturity, pod number, pod length, seed number and 100-seed weight. Accessions differed significantly for the principal phenological and reproductive traits, whereas branch number and pods per ten plants did not differ significantly. Days to 50% flowering ranged from 47.67 to 58.33 days, while 95% pod maturity ranged from 83.00 to 96.33 days. IT16K-2556-1 was earliest to 50% flowering, and IAR-24R-156-5 was earliest to 95% pod maturity. IT17K-850-1-1 produced the highest pod number (234.33 pods per ten plants), whereas IT17K-1589-3-1 combined the longest pods (18.19 cm) with the highest 100-seed weight (25.44 g). Days to first flowering were strongly correlated with days to 50% flowering (r = 0.905, P < 0.001) and first pod maturity (r = 0.960, P < 0.001). Pod length was positively associated with seeds per ten pods (r = 0.500, P < 0.05) and 100-seed weight (r = 0.445, P < 0.05). The accessions showed distinct phenological and reproductive strategies useful for parent selection and subsequent multi-environment testing. Grain-yield and stability trials are required before recommending any accession for broad cultivation.