Abstract
In order to establish an efficient regeneration system re-quired for production of transgenic plants in the genus lpomoea, several culture media and methods were tested for embryogenic callus induction and plant regeneration in diploid I. tritida, the closest relative of sweet potato. Both of the two 2, 4-D-containing media resulted in the formation of embryogenic calli from shoot meristems, although at slightly different rates (40-56 o/o ). Genotype differences in embryogenic potential were found, with lines HI04-28 and H45-14 giving relatively high frequencies of embryogenic calli. In HI04-28, plant regeneration from embryogenic calli was achieved either through immediate transfer of calli to regeneration medium or through transfer of calli first to ABA-containing embryo production medium then to regeneration medium. Considerable number of plants were obtained in both methods, but immediate transfer of calli to regeneration medium gave a higher rate of plant regeneration. All the different MS-based regeneration media tested, whether hormoneless or containing NAA, were able to regenerate whole plants. The regeneration rates obtained froun the embryogenic calli were among the highest rates so far obtained from in vitro culture of lpomoea.
