In Vitro Selection And Identification Of Salt-tolerant Mutants In Sweetpotato, Ipomoea Batatas (L.) Lam.

In vitro selection of salt-tolerant mutants in sweetpotato cvs. Lizixiang and Xushu 18 was systematically studied by using NaCl as selection stress. Embryogenic suspension cultures of Lizixiang and Xushu 18 were irradiated with gamma ray of 80 Gy, and 1 week after irradiation, they were cultured in MS medium containing 2.0% NaCl and 2.0mg/L 2,4-D for in vitro selection. Salt-tolerant cell aggregates of Lizixiang and Xushu 18 up to 270 and 75, respectively, were obtained. The salt-tolerant cell aggregated obtained were cultured on MS medium supplemented with 2.0mg/L 2.4-D but without NaCl and formed embryogenic calluses. These embryogenic calluses were transferred to MS medium supplemented with 2.0% NaCl and 1.0mg/L ABA, and 223 and 36 embryogenic calluses with somatic embryos were produced in Lizixiang and xushu 18, respectively. The embryogenic calluses with somatic embryos were further transferred to the basal medium, resulting in the regeneration of 276 and 40 salt-tolerant variants in Lizixiang and Xushu 18, respectively.Thirty plants and 10 plants sampled randomly from salt-tolerant variants and control plants of Lizixiang, respectively, were cultured on MS medium supplemented with 0.5%, 1.0%, 1.5% or 2.0% NaCl. The results indicated that the salt-tolerant variants showed better growth than the control plants. After 4 weeks for 0.5% NaCl treatment, 160 salt-tolerant variants of lizixiang were analyzed for SOD and proline, and it was found that the SOD value of 29 variants was significantly higher than that of the control and the proline content of 51 variants was significantly higher that of the control. The variants higher than the control at the SOD value and proline content were 7 plants. In comparison with the control, obvious differences of peroxidase isozyme patterns existed in 14 of the 51 variants with high proline content and obvious differences of esterase isozyme patterns existed in 19 of the 51 variants with high proline content. These 51 variants were further analyzed by RAPDs, resulting in that 3 of 20 RAPD primers generated different profiles in 3 variants compared to the control plants.