Physiological assessment of terminal drought stress tolerance in extra-early maturing cowpea (Vigna unguiculata) genotypes

Abstract

Nearly 38% of the cowpea area in sub-Saharan Africa experiences terminal drought that can slash grain yield by more than half. This research evaluated 18 extra-early maturing cowpea genotypes for physiological traits linked to drought tolerance at KNUST, Kumasi, during the 2023 minor season. A split-plot design with irrigation regime (well-watered and terminal drought from 40 DAS) as main plot and genotype as subplot was replicated three times. Relative water content, proline, chlorophyll fluorescence, SPAD index, stomatal conductance, and water-use efficiency were measured at pre-flowering and pod-filling stages. Three genotypes—IT97K-499-35, IT98K-205-8, and TVu-14196—maintained RWC above 72% and proline exceeding 35 µmol/g under stress, classifying them as highly tolerant. Grain yield loss in this group averaged 19.3%, against 57.8% in the highly susceptible class.