Evaluation of drought tolerance in cotton (Gossypium hirsutum L.) genotypes under irrigated and rainfed conditions

Drought stress is a critical constraint to cotton (Gossypium hirsutum L.) productivity, particularly in rainfed cultivation areas. This study assessed the drought tolerance of twenty cotton genotypes under irrigated and rainfed conditions during the 2006-2007 growing season. The trial was conducted using a randomized complete block design (RCBD) with three replications. Morphological, physiological, and yield-related traits were measured, including plant height, boll number, boll weight, seed cotton yield, relative water content (RWC), and total dry matter. Drought tolerance was further quantified using stress indices: Drought Susceptibility Index (DSI), Yield Stability Ratio (YSR), and Plant Height Stress Index (PHSI). Results showed significant genotypic variation under water-limited conditions. The average yield reduction under drought was 13.37%, with GSHV-99/291, GK-147, SSB-5, and ARB-815 demonstrating superior performance through minimal yield loss, stable RWC, and favorable stress indices. In contrast, PH-1009, KH-138, and LRA-5166 were more susceptible to drought, exhibiting greater reductions in yield and physiological parameters. Heatmap analysis effectively grouped genotypes based on multivariate trait responses, aiding the visual classification of drought-tolerant and susceptible lines. These findings highlight the potential of specific genotypes for deployment in drought-prone areas and their use in breeding programs aimed at improving cotton resilience under limited water availability.