Morphological, Physiological and Antioxidant Responses of Five Dryland Maize (Zea mays L.) Genotypes to Water-Deficit Stress

Maize (Zea mays) is a critical staple for global food security, particularly in developing nations facing a projected population increase to 9.7 billion by 2050, necessitating enhanced agricultural productivity and drought-resilient cultivars. This study provides a comprehensive evaluation of the morphological, physiological, and antioxidant responses of five South African dryland maize genotypes (CY1 DKC71-44B, CY2 DKC72-76BR, CY3 DKC74-26R, CW1 DKC75-65BR, and CW3 DKC78-45BRGEN) to drought stress and identifies genotype-specific antioxidant mechanisms associated with drought tolerance. Morphological (shoot growth), physiological (relative water content—RWC), and biochemical (hydrogen peroxide—H2O2, lipid peroxidation, ascorbate peroxidase—APX, and superoxide dismutase—SOD activity) parameters were assessed to identify drought tolerance mechanisms. Drought stress significantly reduced shoot length (28–41%), fresh biomass (up to 41%), and relative water content (19–22%) across the evaluated maize genotypes. However, CY3 (DKC74-26R) and CW3 (DKC78-45BRGEN) maintained higher tissue hydration, suggesting superior drought adaptation. Water deficit also induced oxidative stress, resulting in increases in hydrogen peroxide and lipid peroxidation of up to 245%. In response, APX and SOD isozyme activities increased under drought stress, as demonstrated by enhanced in-gel activity and pixel intensity values. Native-PAGE analysis further revealed differential induction of APX and SOD isoforms, indicating genotype-specific antioxidant responses to drought stress. This study provides critical insights for breeding drought-resilient maize varieties for South Africa’s climate, improving agricultural productivity despite growing climatic variability.