Somaclonal Variation In Embryogenic Suspension Cultures Of Sweetpotato, Ipomoea Batatas (L.) Lam.

Embryogenic suspension cultures of sweetpotato cv. Xushu 18 were established through the use of the three different shoot tips. The somaclonal variation in the process of embryogenic suspension cultures and plant regeneration was investigated systematically.Shoot tips of about 0.5 mm in length gave rise to embryogenic calluses on MS medium supplemented with 2.0 mg·L(-1) 2,4-D. The obtained embryogenic calluses were used to initiate cell suspension cultures in MS medium containing 2.0 mg·L(-1)2,4-D. Rapidly-growing and well-dispersed cell suspension cultures were established. Sixteen weeks, twenty weeks, and twenty-four weeks after the initiation of suspension cultures from the three different shoot tips, cell aggregates about 1.0 mm in diameter were transferred to MS agar medium supplemented with 2.0mg·L(-1) 2,4-D and formed embryogenic calluses with somatic embryos. The embryogenic calluses with somatic embryos were further transferred to MS agar medium supplemented with 1.0 mg·L(-1) ABA, resulting in the germination of somatic embryos. The frequencies of plant regeneration reached 100% in all three shoot tips. The calluses with somatic embryos and plantlets were further transferred to the basal medium, resulting in the regeneration of 289,540, and 971 plants from three different shoot tips, respectively.From the 1800 regenerated plants of Xushu 18, 525 plants were sampled randomly for the isoenzyme analysis. The results showed that obvious variations in peroxidase isozyme patterns were found in 11 of the 525 plants (2.095 %), obvious variations of esterase isozyme patterns existed in 12 of the 525 plants (2.286 %), and in the 4 plants (0.762 %) obvious variations of both isozyme patterns were observed in comparison with the control. RAPD analysis was conducted for the 19 isoenzyme variants and the 90 plants sampled randomly from the 1800 regenerated plants. It was indicated that 20 of the 30 RAPD primers used generated different profiles in 58 of the 90 plants (64.444 %) compared to the control plants; and all the 30 RAPD primers used generated different profiles in 17 of the 19 isozyme variants compared to the control plants. The regenerated plants were transplanted in a field. Variations of leaf vein color and root skin color were observed in 0.500 % and 3.944 % of the regenerated plants, respectively. Analysis for the dry matter content demonstrated that the dry matter content was also changed in a part of the regenerated plants.