Selection for salt tolerance in cotton tissue culture and plant regeneration from NaCl-tolerant embryogenic callus

Cotton embryogenic calli that were subcultured for at least one year were t ransferred to modified MS medium supplemented with 5-40 g/L NaCl for select ing salt-tolerant callus. The NaCl-tolerant calli were obtained by continuo us selection on modified MS medium supplemented with various concentrations of NaCl. NaCl influenced not only the callus growth, survival, and morphol ogy, but also somatic embryogenesis and plant regeneration, The half-lethal concentration of NaCl was between 5g/L and 10g/L; the lethal concentration of NaCl was 40g/L on cotton embryogenic callus. NaCl-tolerant callus grew relatively well on MS medium supplemented with 10g/L NaCl. Somatic embryos resistant to 20 g/L NaCl and regenerated plantlets resistant to 15g/L NaCl have been obtained. The selected tolerant callus and the reinitiated callus from the tolerant regenerated plant showed a hi-her tolerance to osmotic s tress than the non-selected callus. The key factor for successfully obtaini ng salt-resistant regenerated plants was to select mutants from over one-ye ar-old embryogenic calli.