Physiological characterization of gamma-ray induced salt tolerant rice mutants

High salinity in soil is one of the major abiotic stresses leading to the reduction of rice yield. In this study, two salt-tolerant rice mutants induced by gamma-irradiation were selected for in vivo and vitro screening techniques, and their physiological characteristics were evaluated. Using a salt stress screening based on the Standard Evaluation System, 2 candidate lines for salt tolerance (ST-87 and ST-301) were selected out of 1,500 M6 mutant lines. The two ST-lines were further characterized through a physiological analysis, which examined factors such as the electrolyte leakage (EL), malondialdehyde (MDA), antioxidant, chlorophyll, total amino acid, and Na/K contents. Compared with the WT, the ST-lines demonstrated lower levels then the activity of the enzymatic catalase in the contents of EL and MDA and the higher peroxidase under the salt condition. The chlorophyll and total carotenoid contents decreased more severely in the WT-lines than in those of the ST-lines. The total amino acid contents in the seedling leaves of the ST-lines were 2.2 and 1.4-times higher than in the WT. In the ratio of K/Na of the ST and WT-lines, the ST87 (2.7 fold) was significantly higher than that of the WT (1.4 fold). The selected rice mutant lines in our study will be used to increase the salt tolerance in the rice breeding program. Also, the screening methods used in this study will help to develop an excellent variety of rice with a tolerance to salt.