ABSCISIC ACID-INDUCED GROWTH-INHIBITION OF SWEET-POTATO (IPOMOEA-BATATAS L) INVITRO

The inhibitory effects of abscisic acid (ABA) on in vitro growth and development of axillary buds from nodal segments of sweet potato (Ipomoea batatas L.) was investigated. ABA at concentrations of 0.01, 0.1, 1.0 or 10.0 mg l-1 inhibited axillary bud and root development and subsequent plantlet growth. ABA at 10 mg l-1 completely inhibited axillary shoot development but did not affect the viability of cv. Jewel explants over a culture period of 365 days. Transfer of nodal segments cultured for 90, 180 or 365 days from basal medium containing 10 mg l-1 ABA to growth regulator-free media resulted in rapid and normal plantlet development. Gibberellic acid at 0.1, 1.0 or 10.0 mg l-1 in the presence of ABA at 0.1, 1.0 or 10.0 mg l-1 did not counteract the ABA-induced growth inhibition. Although ABA totally inhibited the growth of 6 sweet potato plant introductions at a concentration of 10.0 mg l-1, the efficacy of ABA as a suppressant of shoot growth varied with genotype.