Micropropagation of Dioscorea alata (cv. wonago I) from shoot tips and nodal explants

Abstract

Dioscorea alata L. (Yam) is a member of genus Dioscorea and monocotyledonous plant belonging to the Dioscoreaceae family which comprises about 600 species. D. alata is an important corp plant that produces tuberous roots used as a source of food and medicine. Inefficiency of traditional methods of propagation and lack of planting materials are the main constraints for implementing large-scale cultivation. The purpose of this study was, therefore, to develop a micropropagation protocol for D. alata L. from shoot tip and nodal explants. Explants were sterilized using different concentrations of NaOCl for different time exposure. MS culture media supplemented with different types and concentration of auxins and cytokinins were used for culture initiation, shoot multiplication and root induction. Sodium hypochlorite (NaOCl, 5.2% of active chlorine) at a concentration of 5 and 2 % at exposure time of 5 and 20 minutes gave 76.60±0.36%, of survived explants for nodal and 72.66±0.85% for shoot tip respectively. The initiation media with a combination of 4x4x2x2 factorial; and multiplication of 3x3x2x2 factorial were used. From these, BAP of 1.5 mg/l + NAA of 1.0 mg/l gave 93.2% for nodal and BAP of 1.0 mg/l + NAA of 1.0 mg/l gave 87.1% for shoot tip was found to be an optimum concentration for shoot induction. The combination of 2.0mg/l KIN, 1.0mg/l BAP and with 0.5mg/l NAA and 2.0mg/l KIN, 0.5mg/l BAP and with 0.5mg/l NAA was found to be the optimum concentration yielding 8.4± 0.21% and 9.5± 0.29% shoots per explants for shoot tip and nodal respectively for shoot multiplication. Half strength MS medium with 2.0 mg/l IBA gave the highest rooting percentage and with 2.0mg/l NAA gave optimum root number and length. Up on acclimatization and transplanting, 90% survival efficiency was observed on soil mix ratio of 2:2:1 decomposed coffee husk, sand and red soil respectively. There were no observable variations with respect to morphology and growth characteristics to the greenhouse raised parent plant. The results obtained in this study permit the development of mass propagation protocol that could enable large scale commercial production of this highly demanded Dioscorea cultivar and provide a possible system towards genetic improvement of the crop.