Clonal Propagation through Bulbils in Dioscorea opposita Thunb. cv. Yamatoimo

Abstract

For establishing clonal propagation through bulbils in Dioscorea opposita cv. Yamatoimo, stem segments with a node of lateral shoots were cultured aseptically on Murashige & Skoog(M. S) basal medium supplemented with sucrose (20g/l or 40g/l) and growth regulators, 6-benzylaminopurine(BA), α-naphthaleneacetic acid (NAA) and abscisic acid(ABA).
The cultures were kept under a schedule of 14 hours light(2000lx): 10 hours dark at a constant temperature of 25°C.
1. Effect of BA and NAA on bulbil formation: Stem segments were inserted upright or inverted in M. S and 1/2 M. S (-NH₄NO₃) basal medium. There was no significant difference on bulbil formation between the stem segments inserted upright and those inverted in BA stimulated sprouting of axillary bud, which were observed in the node of stem segments, but inhibited bulbil formation. NAA stimulated bulbil formation at concentrations of 0 to 1mg/l, but was inhibitory at 10mg/l.
2. Effect of length of stem segments on bulbil formation: There was no significant difference between 1, 2 and 3cm long stem segments in inducing bulbil formation. However, the growth of bulbils was significantly different, being best with 3cm long stem segments.
3. Effect of ABA on bulbil formation: ABA was effective in inducing bulbil formation, and 100% bulbil formation was obtained at 1mg/l.
4. Effect of concentration of M. S medium on bulbil formation: Six types of the basal medium, M. S, M. S(-NH₄NO₃), 1/2 M. S, 1/2 M. S(-NH₄NO₃), 1/5 M. S and 1/5 M. S(-NH₄NO₃) were tested for their effect on bulbil formation. 1/2 M. S basal medium gave the highest percentage of bulbil formation, followed by 1/2 M. S (-NH₄NO₃) and M. S basal medium, but there was no significant difference between them. 1/5 M. S and 1/5(-NH₄NO₃) basal medium were inferior to the others in terms of bulbil formation, but were effective for the sprouting of axillary buds.