Drought stress is one of the major abiotic stresses affecting lint yield and fibre quality in cotton. With increase in population, degrading natural resources and frequent drought occurrences, development of high yielding, drought tolerant cotton cultivars is critical for sustainable cotton production across countries. Six Gossypium hirsutum genotypes identified for drought tolerance, wider adaptability and better fibre quality traits were characterized for various morpho-physiological and biochemical characters and their molecular basis was investigated under drought stress. Under drought conditions, genotypes revealed statistically significant differences for all the morpho-physiological and biochemical traits. The interaction (genotype × treatment) effects were highly significant for root length, excised leaf water loss and cell membrane thermostability indicating differential interaction of genotypes under control and stress conditions. Correlation studies revealed that under drought stress, relative water content had significant positive correlation with root length and root-to-shoot ratio while it had significant negative correlation with excised leaf water loss, epicuticular wax, proline, potassium and total soluble sugar content. Analysis of expression of fourteen drought stress related genes under water stress indicated that both ABA dependent and ABA independent mechanisms of drought tolerance might be operating differentially in the studied genotypes. IC325280 and LRA5166 exhibited ABA mediated expression of stress responsive genes and traits. Molecular basis of drought tolerance in IC357406, Suraj, IC259637 and CNH 28I genotypes could be attributed to ABA independent pathway. Based on physiological phenotyping, the genotypes IC325280 and IC357406 were identified to possess better root traits and LRA5166 was found to have enhanced cellular level tolerance. Variety Suraj exhibited good osmotic adjustment and better root traits to withstand water stress. The identified drought component trait(s) in specific genotypes would pave way for their pyramiding through marker assisted cotton breeding.

干旱胁迫是影响棉花皮棉产量和纤维质量的主要非生物胁迫之一。随着人口的增加、自然资源的退化和干旱的频繁发生，开发高产、耐旱的棉花品种对于各国的可持续棉花生产至关重要。六地棉鉴定出耐旱性、更广泛的适应性和更好的纤维品质性状的基因型具有各种形态生理和生化特征，并在干旱胁迫下研究了它们的分子基础。在干旱条件下，基因型揭示了所有形态生理和生化性状的统计学显着差异。相互作用（基因型×处理）对根长、离体叶片失水和细胞膜热稳定性的影响非常显着，表明在控制和胁迫条件下基因型的不同相互作用。相关研究表明，干旱胁迫下，相对含水量与根长、根冠比呈显着正相关，与离体叶片失水呈显着负相关，表皮蜡、脯氨酸、钾和总可溶性糖含量。水分胁迫下 14 个干旱胁迫相关基因的表达分析表明，ABA 依赖性和 ABA 非依赖性耐旱机制在所研究的基因型中可能存在差异。IC325280 和 LRA5166 表现出 ABA 介导的应激反应基因和性状的表达。IC357406、Suraj、IC259637 和 CNH 28I 基因型耐旱的分子基础可归因于 ABA 非依赖性途径。基于生理表型，基因型 IC325280 和 IC357406 被鉴定为具有更好的根性状，并且发现 LRA5166 具有增强的细胞水平耐受性。品种 Suraj 表现出良好的渗透调节和更好的根系特性以承受水分胁迫。