Protocol Development for Micropropagation of the Widely Cultivated Ethiopian Yam (Dioscorea spp., Bulcha variety)

Abstract

Yam (Dioscorea species) is a monocotyledonous tuber forming tropical vine, which belongs to the order Liliflorae, family Dioscoreaceae, and genus Dioscorea. Yam is well known for its medicinal use as well as nutritional values. Conventional propagation of yam (Dioscorea spp.) is limited due to low propagation rates. Hence, in vitro propagation is the best alternative to overcome such limitations of conventional propagation. The present study reports a high and cost effective micropropagation protocol for Ethiopian yam (Dioscorea alata, Bulcha variety) and used for high and efficient plantlet regeneration from 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) at a concentration of 1% at exposure time of 15minutes gave the highest percentages (100%) of survived explants. The combination of 0.5 BAP with 1mg/l NAA was found to be an optimum concentration for shoot induction. BAP at 1.5 mg/l was found to be the optimum concentration for shoot multiplication, yielding 7.28±0.07 shoots number perexplant with a shoot length of 8.72±0.43 cm. MS medium with 2.0 mg/l NAA with 1.5 mg/l IBA gave the highest rooting percentage and gave optimum root number (10.6±0.44) and root length (13.80±0.44). Finally, for acclimatization, in vitro multiplied plantlets were transferred to greenhouse for hardening off. In vitro raised plantlets were acclimatized and recorded 90% of survival rate on soil medium with combination ratio of 1:2:1 top soil, sand soil and compost, respectively. Finally use of the already developed micropropagation protocol for large scale production of the Bulcha varieties and distributing to farmers to increase yam tuber production in Ethiopia should be given due attention.