Selection and characterizations of radiation-induced salinity-tolerant lines in rice

NaCl tolerant cell lines were selected from irradiated callus, which were generated from seed cultures. M1-regenerates were obtained from the salt-tolerant callus cultured on the auxin-free medium for 30 days. Some regenerants were more tolerant than the parent variety (Dongjinbyeo) on a medium containing 0.75 % NaCl. Seeds (M3 5,000 lines) derived from M2 lines were grown to the 3 leaf stage. M3 lines were soaked with a 0.75 % salt solution for 3 weeks and 350 salt-tolerant genotypes were selected. Among the M3 350 lines, forty tolerant lines were selected from a saline field (10~14 mS) near the sea coast. Of the forty lines, two lines (18-1 and 50-1) showed more improved plant height, panicle length, tillering number, spikelet number and yield than those of the original variety. Thirty primers were screened and two RAPD markers were identified, which appeared in both the salt-tolerant lines (18-1 and 50-1). From DNA-hybridization experiments, it appeared that the fragment arose from the middle-repetitive copy sequences. The transcript involved in the marker showed a higher expression in the salt-tolerant lines than the sensitive lines. The salt-tolerant lines would be useful as a resource for salt-tolerant breeding.