Cotton (Gossypium spp.) is vital raw product for the global textile industry. Its production is affected by drought stress, exacerbated by climate change. This study was designed to investigate the physiological and biochemical responses of cotton genotypes to drought, aiming to identify mechanisms of drought tolerance and susceptibility. Within a glasshouse, diverse genotypes were grown in polythene bags with a soil-sand mix, subjected to three drought stress levels i.e., control (100% field capacity), moderate stress (75% field capacity), and severe stress (50% field capacity), in a two-factor factorial design under a Completely Randomized Design (CRD). Physiological measurements and biochemical assays under varying drought conditions revealed significant decreases in growth related traits (shoot and root lengths, fresh and dry weights) with increased drought severity. Alongside antioxidant defence mechanisms were upregulated, as evidenced by increased Peroxidase (POD), Catalase (CAT), Superoxide Dismutase (SOD) activities, and proline levels, indicating adaptive responses to oxidative stress. Principal Component Analysis (PCA) showed the results for that the first two principal components accounted for approximately 71.83% of the variance, summarizing the major contribution by genotypes' drought responses. Cluster analysis further delineated the genotypes into three clusters, representing distinct drought response strategies. Notably, Cluster 1 (e.g., MNH-554, FH-113, FH-682, VH-295, AA-802) exhibited robust drought tolerance, whereas Cluster 3 (e.g., FH-114, FH-901, IR-3, MNH-552) included more drought-susceptible genotypes. This study revealed the complex dynamics between cotton's genetic makeup, physiological responses, and biochemical processes in facing drought conditions and to ascertain the drought tolerant and susceptible genotypes.

Keywords: Cotton, drought stress, drought seedling, morpho-physiological, proline, catalase