Nodal explants of 12 accessions from four species of yam (Dioscorea spp.) were cultured for six weeks on MS to evaluate the influence of IAA, Kn, NAA and BAP on the production of leaves and microtubers. Four Dioscorea polystachya Turcz., three each of D. bulbifera L. and D. sansibarensis Pax. and two D. japonica Thunb. accessions were used. Five and 10 mg/l of Kn along with IAA and sucrose, and 0.2 and 0.5 mg/l of NAA, sucrose and with or without BAP were used in four treatments. The accessions Yam 23 and Yam 25 of D. sansibarensis failed to initiate any leaf under four treatments. The remaining accessions produced 0.11 to 1.76 leaves per explant. The medium containing IAA with higher concentration of Kn (10 mg/l) and 3% sucrose was found to be best for in vitro production of leaf (0.71/explant) and the most productive species was D. japonica (1.36), followed by D. polystachya (1.19/explant). At the same culture period, Yam 16 of D. bulbifera failed to initiate any microtuber at IAA with Kn, and NAA with or without BAP. The remaining accessions produced 0.09 to 1.15 microtubers per explant. Lower concentration of Kn (5 mg/l) with IAA and sucrose was favourable for producing microtubers (0.61/explant on an average), the best species being D. sansibarensis (1.27) followed by D. japonica (0.59/ explant). Finally, the presence of BAP adversely affected the production of microtuber among Dioscorea species. Key words: Dioscorea spp., Microtuber, Nodal culture, Propagation D.O.I. 10.3329/ptcb.v18i1.3260 Plant Tissue Cult. & Biotech. 18(1): 25-35, 2008 (June)
Effects of Growth Regulators on In vitro Propagation and Tuberization of Four Dioscorea Species