OXIDATIVE STRESS RESPONSES AND ANTIOXIDANT DEFENCE AS INDICATORS OF DROUGHT TOLERANCE IN EXTRA-LONG STAPLE COTTON GENOTYPES
Abstract
Extra-long staple cotton (Gossypium barbadense L.) is a strategically important industrial crop in Central Asia, where drought reduces yields by 40–60% and constitutes the principal abiotic constraint on productivity. Under water deficit, an imbalance between reactive oxygen species (ROS) generation and antioxidant neutralisation leads to oxidative stress, manifesting as lipid peroxidation, pigment degradation, and cellular damage. Elucidating the biochemical basis of drought tolerance at early ontogenetic stages is essential for developing cost-effective germplasm screening approaches applicable in breeding programmes. The antioxidant system responses of four G. barbadense L. genotypes - drought-tolerant cultivar Surkhan-103 and three breeding lines (L-157, L-474, L-1000) - were investigated under PEG-6000-induced osmotic stress (10%) at the cotyledon stage. Catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) activities, alongside malondialdehyde (MDA), hydrogen peroxide (H₂O₂), chlorophyll a and b, and carotenoid contents, were determined at 0, 6, 12, and 24 h post-stress initiation. Each treatment included three independent biological replicates; data were analysed by one-way ANOVA and LSD test (p < 0.05).
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