Physiological traits and related gene expression of salt tolerance in hybrid rice Jingliangyou 3261 at the seedling stage

Abstract Background Soil salinity severely restricts rice growth and productivity, particularly at the seedling stage when plants are highly sensitive to ionic and osmotic stress. Results In this study, we systematically evaluated the phenotypic, physiological, and molecular responses of the hybrid rice cultivar Jingliangyou 3261 under salt stress. Compared with the control cultivars ( Yuxiangyouzhan , Huazhan , and Jingliangyouhuazhan ), Jingliangyou 3261 seedlings exhibited significantly higher survival rates, less leaf chlorosis, and stronger recovery after stress relief. Physiological analyses indicated smaller declines in chlorophyll content, reduced malondialdehyde (MDA) accumulation, and enhanced synthesis of soluble proteins. Moreover, Jingliangyou 3261 maintained superior ion homeostasis by limiting Na⁺ accumulation and sustaining higher K⁺ levels, resulting in a relatively stable Na⁺/K⁺ ratio. Antioxidant capacity was enhanced, as reflected by elevated superoxide dismutase (SOD) and peroxidase (POD) activities together with reduced reactive oxygen species (ROS) accumulation. Molecular analysis showed that under salt stress, osmotic adjustment genes ( OsP5CS1/2 , OsLEA3 ), ion transport genes ( OsHKT , OsNHX , OsHAK , OsKAT , OsSOS1 ), and antioxidant-related genes ( OsCSD , OsCAT , OsAPX ) were significantly up-regulated in Jingliangyou 3261 . Conclusions These coordinated physiological and molecular responses provide a comprehensive mechanistic basis for the superior salt tolerance of Jingliangyou 3261. Our findings not only deepen the understanding of salt tolerance mechanisms in hybrid rice but also provide valuable genetic resources for salt-tolerant breeding and the utilization of saline–alkali soils.