In vitro breeding for salt tolerant rice Ⅰ. Selection of salt tolerant callus and regeneration

Feasibility of selecting salt-tolerant callus and its subsequent regeneration to plant were studied. Callus induction was retarded at 0.6-1.2% NaCl and greatly impaired at 1.5% NaCl. No callus was formed at or above 1.8% NaCl. Marked varietal difference in callusing ability on salt medium was observed and callus induction efficiency ranged from 38.2% to 84.4%, averaging about 57%. Some callus showed stable growth throughout three selective passages and regenerated into plantlet after transfered on to regeneration medium. A total of 35 regenerated plants were died within 10 days after transplanted on to pot except two plants in Calrose 75. None of the 427 R2 plant derived from the two plants survived after transplanted on to pot was exibited salt tolerance in seedling test at 0.6% NaCl.