Comparative analysis of salt tolerance in cotton cultivars under saline water stress

Soil salinity imposes multiple stresses on cotton (Gossypium spp.) and the use of saline water for irrigation is common in coastal regions. However, the effects of borewell saline water (NaCl) on cotton cultivars remains underexplored. A pot experiment conducted during 2017-2018 aimed to evaluate the morphological, biochemical and physiological responses of six cotton cultivars- G. herbaceum (G-Cot 25, Jayadhar), G. arboreum (Phule dhanwantry, Roja) and G. hirsutum (Suraj, LRA-5166) subjected to NaCl treatments (100, 150 and 200 mM) and a control. All cultivars exhibited a progressive decline in growth parameters with increasing salinity. Among them, Jayadhar and Suraj demonstrated the highest tolerance, maintaining superior growth and physiological performance under NaCl stress. Relative water content decreased significantly across all cultivars; however, G-Cot 25 and LRA-5166 retained higher water content under saline conditions. Biochemically, NaCl stress resulted in reduced levels of total chlorophyll and carotenoids, alongside an increase in protein content, suggesting adaptive responses to salinity. Jayadhar, Suraj and Phule Dhanwantry exhibited greater chlorophyll retention, indicating enhanced biochemical stability. Malondialdehyde (MDA) levels increased under salinity, signifying lipid peroxidation; however, Jayadhar and Suraj accumulated lower MDA levels, suggesting reduced oxidative damage. Proline content increased in all cultivars, with Jayadhar and Suraj showing the highest accumulation, reflecting improved osmotic adjustment. Activities of antioxidant enzyme including superoxide dismutase, catalase and peroxidase were significantly enhanced, particularly in G-Cot 25, Jayadhar and Phule dhanwantry respectively. These findings indicate that antioxidant defense mechanisms play a crucial role in mitigating oxidative damage by scavenging reactive oxygen species under saline conditions. Based on an integrative assessment, the G. herbaceum cultivar Jayadhar demonstrated the highest tolerance to salinity.