Objective  Physiological response and molecular mechanism of different salt-tolerant rice lines in dealing with high salt stress were studied to facilitate screening and breeding resistant varieties.

  Methods  Salt-tolerant rice X1, X2, and X3 as well as salt-sensitive X20 and X30 were treated by a high salt condition of 1/2KB solution with 200 mmol·L⁻¹ NaCl. The physiological metabolism and expression of functional genes of the two contrasting groups of rice were compared.

  Results  Under the stress, the proline and soluble sugar contents, superoxide dismutase and catalase activities, and expressions of OsP5CS1, OsProt, OsCu/Zn-SOD, OsAPX2, OsNCED3, and OsNCED5 of the salt-tolerant rice were significantly higher, whereas the malondialdehyde and hydrogen peroxide contents significantly lower, than those of the salt-sensitive counterparts.

  Conclusion  The salt-tolerant rice lines resisted the high salt exposure mainly by increasing osmotic regulation, activating oxygen scavenging, and accentuating functional gene expression of the plants.