ABSTRACT :

Plant growth regulator supplements into the nutrient medium is one of the most influential factors
affecting efficiency of in vitro propagation. While benzyladenine (BA) has been extensively studied, no information is available on sweet potato (Ipomoea batatas, L.) responses to thidiazuron (TDZ). Current study used explants prepared from proliferating shoots of established axenic cultures of two cvs (11 and 44). Explants were incubated on agar solidified (0.7% g) Murashige and Skoog (MS) medium
containing 3% sucrose and supplemented with 5μM BA or 0.5 μM TDZ or used free of BA and TDZ (MS-0, control). Data suggesting that BA and TDZ were indispensable for in vitro propagation of sweet potato since no excisable shoot were produced on MS-0 medium. BA was more effective than TDZ in inducing multiple shoot buds but only one shoot developed to well excisable shoot from such multiple shoot-buds. Responses to BA and TDZ were cultivar-dependent for percentage of explants excisable shoot which was higher on BA-medium in cv 11 while on TDZ-medium for cv 44. The harvested shoots from BA-medium had 13 leaves and those produced on TDZ-medium developed 10 leaves. In vitro rooting was not necessary since non-rooted shoots were capable to root while acclimatized to ex-vitro conditions. Cultivar 11 showed 100% survival after ex-vitro acclimatization whether on BA or TDZ medium. All plantlets of cv 44 produced on TDZ medium survived the ex-vitro acclimatized while those from BA medium showed 87% survival rate. It is proposed that culture of 12 single nodal axillary-buds prepared during September from growing sweet potato cv. 11 in the production field would produce transplants to grow one feddan (25,000) next season (April) after 4 sequential cycles of in vitro propagation on BA-medium. For cv. 44, starting with 25 axillary buds cultured on TDZ-medium would be needed. The described protocol may be useful to establish micropropagation industry of sweet potato that to help in overcoming difficulties of conventional vegetative propagation for this crop species.