The world is currently facing a critical water shortage, posing a major threat to food security. Wheat, one of the most essential staple crops, is particularly vulnerable to drought stress. Wild wheat species, Aegilops tauschii, serve as a valuable genetic resource for improving drought tolerance due to their physiological and molecular adaptability. This study aimed to investigate the physiological, biochemical, and gene expression responses of ABA-responsive genes in different genotypes of Aegilops tauschii under varying levels of drought stress. Six wild wheat genotypes were exposed to three drought levels (100 %, 70 %, and 40 % field capacity). Measured biochemical and physiological traits included chlorophyll content, root and shoot size, proline, phenols, flavonoids, carotenoids, and oxidative stress markers (MDA and H2O2). Antioxidant enzyme activity (POX, CAT, SOD) and the expression of drought-related genes (PHV A and HVA22) were also evaluated. Drought stress significantly reduced physiological traits, including chlorophyll content and plant growth, while enhancing stress-related metabolites. Severe drought (40 % FC) induced sharp increases in proline, phenols, and flavonoids across all genotypes. Carotenoid concentration rose in Taushi B3, whereas Taushi C1 and Taushi Y1 maintained leaf area and chlorophyll levels under moderate drought. Antioxidant enzyme activity was highest in Taushi A1 and Taushi AX, indicating superior defense against oxidative stress. Gene expression analysis revealed upregulation of PHV A and HVA22 under drought, highlighting genotype-specific responses. These findings demonstrate the genotype-dependent adaptability of Aegilops tauschii to drought stress through distinct physiological, biochemical, and molecular mechanisms. Specifically, Taushi A1 and Taushi AX showed superior antioxidant defenses, while Taushi C1 and Taushi Y1 maintained stronger physiological stability. These results suggest that Aegilops tauschii genotypes hold significant potential for developing drought-resistant wheat varieties and contribute to global food security under water-limited conditions.
