CHARACTERIZATION OF RICE (ORYZA-SATIVA L) PLANTS REGENERATED FROM SALT-TOLERANT CELL-LINES

Cell lines were established from the seed of two elite US rice lines ( L-202 and M-202) as well as Indica rice varieties Pokkali, IR 28 and I R 42. Salt-tolerant cell lines were selected from these callus culture s by a single step selection process on tissue culture medium containi ng 1% (0.171 M) NaCl. Plants were regenerated from the salt-tolerant l ines. The salt selection process and regeneration of the embryogenic c allus had minimal adverse effect on subsequent plant growth, since the regenerated plants were vigorous, have flowered and in most cases wer e fertile. Seed was collected from the regenerated plants and the germ inated seedlings were tested for salt tolerance. The R2 seedling salt tolerance was compared for plants regenerated from salt selected cell lines of L-202 that had been maintained on 1% NaCl for 1, 4 and 5 mont hs. Heritable improvement in salt tolerance was obtained in R2 seedlin gs from one plant that had been regenerated after 5 months of selectio n on salt-containing medium. These results indicate that short-term sa lt selected rice callus contains many embryogenic calli that do not ca rry heritable changes in the salt tolerance phenotype and therefore ne cessitates screening for the tolerance phenotype in the progeny of the regenerated plants. Thus, as shown in the case of L-202 (R4), prolong ing the selection process in vitro for rice improves the likelihood of regenerating plants with improved salt tolerance.