Comparative analysis of physiological, enzymatic, and genetic responses revealed the differences in salt tolerance between two rice varieties at the seedling stage

Salt stress remains a global problem affecting agricultural production, and the elucidation of stress tolerance mechanisms in crops, such as rice, can provide essential information to breeders to generate improved cultivars capable of withstanding environmental challenges. Therefore, this study aimed to evaluate the tolerance mechanisms of two rice cultivars with different salinity tolerance. The rice cultivars, Sakha Super 300 (SS300, tolerant) and Blue Bonnet 76 (BB76, sensitive), were subjected to 0 and 100 mM NaCl (control and salt stress, respectively) for 14 days. Subsequently, growth indices (dry weight and plant length), physiological parameters (Na+ and K+ concentrations, secondary metabolites, enzyme activities, and chlorophyll and carotenoid concentrations), and the expression of Na+ and K+ transport-coding genes were determined. The results showed that the dry weight (DW) of SS300 was not significantly altered by salt stress, whereas that of BB76 decreased by 1.8 folds. The leaf Na+ concentration in SS300 (15.3 mg/g DW) was less than that of BB76 (23.7 mg/g DW), whereas the ratio of Na+/K+ was significantly higher in BB76 than in SS300 leaves. The leaf proline concentration of BB76 was 23-fold that of control and 9-fold that of SS300, whereas total flavonoid increased only in the leaves of SS300 (38 % increase). Regarding antioxidant enzyme activities, peroxidase (POD) significantly declined (2.7-fold) in the leaves of BB76 but remained unchanged in SS300. Regarding gene expression, there was 21- and 10-fold upregulation of OsHKT1;5 expression in the roots of SS300 and BB76, respectively, whereas root OsAKT1 and OsHAK7 were induced only in SS300 (2.3 and 2-fold induction, respectively). These results suggest that the susceptibility of BB76 to salt stress is likely attributed to the utilization of more energy for osmolyte synthesis, and reduced antioxidants and Na+ and K+ regulation. (c) 2024 SAAB. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.