Influence of carbon source on in vitro tuberization and growth of white yam (Dioscorea rotundata Poir.)

The response of white yam (Dioscorea rotundata Poir.) nodal cuttings to eig ht different carbon sources (sucrose, glucose, mannose, maltose, galactose, fructose, lactose, and sorbitol) at two concentrations (3 and 5%) in modif ied Murashige and Skoog medium was investigated. The number of nodes per pl ant (NNP), plantlet fresh weight, number of leaves per plant (NLP), percent age tuberization, number of micro-tubers per plant (NTP), and micro-tuber w eight per were significantly different among the carbon sources (P < 0.01). There were no significant differences in terms of micro-tuber weight per t uber and plant dry matter content. In terms of NNP and NLP, fructose, gluco se, mannose, and sucrose at 3 and 5%, and sorbitol at 5% were comparable. H owever, nodal cuttings were unable to produce tubers in media containing so rbitol. All the explants cultured in 5% sucrose, 5% fructose, and 3 and 5% mannose produced micro-tubers. The NTP ranged from 0.9 (3% mannose) to 1.8 (5% sucrose), while 5% glucose gave the highest TWP, followed by 5% sucrose , The best carbon sources for in vitro plant (TWP) significant tuberization were sucrose and fructose.