PLANT-REGENERATION OF SWEET-POTATO (IPOMOEA-BATATAS L) FROM LEAF EXPLANTS IN-VITRO USING A 2-STAGE PROTOCOL

Leaf explants of sweetpotato (Ipomoea baratas L. (Lam.)) were cultured on Murashige and Skoog medium (MS) with varying levels (0.2-1 mg l(-1 )) of 2,4-dichlorophenoxyacetic acid (2,4-D; stage I) and transferred to a medium with zeatin riboside (0.2-0.4 mg l(-1); stage II). The hig hest frequency (over 80%) shoot regeneration occurred in the genotype PI 318846-3 cultured on MS + 2,4-D (0.2 mg l(-1)) for 3 days and then transferred to MS + zeatin riboside (0.2 mg l(-1)). Addition of zeatin riboside in the first medium reduced the frequency of shoot regenerat ion. Of the 27 genotypes, 19 exhibited high frequency shoot regenerati on, and eight were completely recalcitrant. The developmental stage of the leaf was critical, as young leaves from the apical portions of th e stem were the most regenerative. Regenerated shoots rooted readily a nd the plants transferred to soil in the greenhouse appeared normal.