Comprehensive Evaluation of Cotton’s Salt Tolerance Based on Growth and Physiological Indicators

Salt stress is one of the environmental factors that limit the growth and development of cotton. Screening salt-tolerant varieties is of great significance for the utilization of salt-tolerant cotton germplasm resources and efficient production in saline land. This study used seven varieties, TH2 (Tahe 2), TH2311, XTM3 (Xintamian 3), XHM1 (Xinhuimian 1), QH18 (Qianhai 18), XLZ61 (Xinluzhong 61), and ZM63 (Zhongmian 63), to investigate the growth and physiological responses of different varieties to salt stress and to comprehensively evaluate their salt tolerance by setting three salt concentrations (0, 0.3, and 0.6%). The results showed that the K+ content of many varieties was significantly reduced under salt stress, such as ZM63, XHM1, XTM3, and TH2311. However, the K+ content in TH2 was significantly increased under salt stress; at 0.6% salinity, the K+ content in QH18 and XLZ61 did not change significantly compared with the control, which may mean that TH2 has a unique ability to regulate potassium homeostasis under salt stress, while QH18 and XLZ61 can maintain relatively normal potassium levels even in a high salt environment. Furthermore, this study found that salt stress significantly reduced the activity of some antioxidant enzymes in most varieties, but some varieties maintained high enzyme activity levels even at a salinity of 0.3%. Compared to the control, QH18 and TH2311 showed no significant change in SOD activity at 0.3% salinity; ZM63 showed no significant difference in POD activity; and XHM1 showed no significant difference in CAT activity. In addition, this study found that QH18, TH2311, and XHM1 exhibited relatively strong salt tolerance among the seven varieties. The research results provide a basis for the screening and utilization of salt-tolerant cotton varieties. Due to the fact that the research results were obtained based on seedling stage data, further research should be conducted in conjunction with multiple growth stages and field experiments to confirm.