In vitro breeding for salt-tolerance rice Ⅲ. Detection of reliable selection criterion for salt-tolerance evaluation

Proline, Na, K and Ca ion contents in the callus cells cultured on the medium with and without NaCl were analyzed to determine reliable selection marker for salt-tolerance evaluation and later in quantitative genetic analysis of salt-tolerance. Even though there was no statistically significant varietal difference in proline content of the callus grown on salt-free medium, proline accumulation ability of the callus was significantly different under salt-stress while the cation contents in the callus grown both on the media with and without NaCl was significantly different. The rank of proline content in the 10 different varietal callus cultured on salt-free medium was highly coincided with the rank of proline accumulation under saline stress but three was no such relationship in case of the cation contents. Larger variability in proline accumulation even under NaCl-stress could provide easier identfication of the salt-tolerant callus. The range of variation in the cation contents was much narrowed under saline condition. Thus measure of proline accumulation in callus may be the most reliable selection criterion for salt-tolerance evaluation.