MORPHO-PHYSIOLOGICAL AND ANTIOXIDANT RESPONSES OF AFRICAN YAM BEAN (Sphenostylis stenocarpa Hochst. Ex. A. Rich Harms) UNDER DROUGHT STRESS CONDITIONS

Drought stress is a major abiotic factor that affects agricultural productivity globally. Drought limits plants growth, physiology, and yield. This study was conducted to evaluate the drought tolerance of nine accessions of African Yam Bean (AYB) (Sphenostylis stenocarpa), a nutrient-rich leguminous crop with potentials for food security in drought-prone regions. The experiment was conducted using standard methods in a greenhouse in a completely randomized design (CRD), with three treatments and three replicates: control, mild drought, and severe drought. Morphological, physiological, biochemical, and growth traits were analyzed. Significant reductions (p ≤ 0.05) were observed in morphological traits under drought stress. Plant height decreased in Ohong (33.3 cm) and Ediba (28.7 cm) relative to control values of 41.3 cm and 29.7 cm, respectively. Leaf area declined in Gakem (32.4 cm²) and Wula (21.3 cm²). Shoot fresh weight dropped in Okpoma (1.4 g) and Adadama (1.6 g) from 4.2 g and 3.8 g, respectively. While most accessions recorded negative relative growth rates (RGR), Ediba maintained a positive RGR (0.002). Ediba and Ohong also exhibited higher peroxidase and catalase activities, while Ukwel and Gakem showed the lowest. The root-to-shoot ratio increased under severe drought, with Ohong (0.36) and Okpoma (0.27) showing the highest adjustments. Drought stress response indices (DSRIs) shows Ediba (10.42) and Ohong (10.54) as the most drought-tolerant accessions. These findings suggest that Ediba and Ohong possess higher drought-resilience traits and thus should be further used in breeding programs that are aimed at improving drought tolerance in AYB and other legumes for sustainable agriculture and food security.