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.
Objectives
We investigated the effects of some growth regulators on in vitro propagation and tuberization of the four species of yam.
Materials
Yam 16 was obtained as aerial tubers from Botanical garden of the Goethe University at Frankfurt Main, Germany. Yam 19 was obtained from the Botanical Garden of the University of Ferrara, and Yam 21 was obtained from the University of Padua both accessions from Italy. The remaining accessions were provided by the In vitro Storage and Cryopreservation Laboratory, IPK, Germany.
Explant
Nodal explants of about 3 cm length were used after removal of the leaf and trimming of the petiole. They were surface disinfected with 70% ethanol and then with sodium hypochlorite (effective chlorine concentration 3 %) and Tween
20 (2 - 3 drops) for 15 min, then rinsed three times in sterile distilled water.