THIDIAZURON-INDUCED ADVENTITIOUS SHOOT REGENERATION OF SWEET-POTATO (IPOMOEA-BATATAS)

Adventitious shoots of sweetpotato (Ipomoea batatas L. Lam.) were prod uced in vitro using a two-stage culture method. Petiole explants were incubated on Murashige and Skoog (MS) medium supplemented with 2,4-dic hlorophenoxy acetic acid (0.2 mg.liter(-1)) for 3 d, and transferred t o MS medium with thidiazuron (0 to 0.4 mg.liter(-1)). Shoot regenerati on was observed in most explants (78.2%) of genotype PI 318846-3 withi n 28 days when cultured on thidiazuron at 0.2 mg liter(-1). Histologic al studies of cultured petiole explants showed meristematic activity w ithin cells of vascular bundles and throughout the ground tissue. Expl ants isolated from apical leaves exhibited higher shoot regeneration f requency than those isolated from the basal portion of the shoot. Leaf lamina explants exhibited lower frequency of regeneration than petiol e explants. In contrast to thidiazuron, the use of zeatin riboside, an d kinetin resulted in a lower frequency of shoot regeneration although more sweetpotato genotypes could be regenerated using either of these two cytokinins. The sweetpotato plants regenerated using thidiazuron grew vigorously and rooted easily when transferred to the greenhouse.