A tissue culture system for callus formation and plant regeneration using tuber discs of Dioscorea tokoro Makino, a pharmaceutical yam species

Abstract

Yam (Dioscorea sp.) is a recalcitrant plant species with respect to plant regeneration in tissue culture. We report here on callus formation and plantlet regeneration in the pharmaceutical yam species D. tokoro Makino. Explants of leaves, nodes, internodes, roots, and tuber discs of three lines of D. tokoro were cultured on media containing the synthetic auxins 2,4-dichlorophenoxyacetic acid or picloram at 10 µM. Explants of nodes, roots, and tuber discs formed calluses at high frequency in all lines we examined, regardless of type of auxin added to the media. However, explants of leaves and internodes rarely formed calluses. Some calluses derived from tuber discs differentiated shoots through the formation of bud-like structures by culture on media with or without 10 µM 6-benzyladenine. The T-1110 line showed the highest shoot formation efficiency. The regenerants from the calluses derived from tuber discs successfully acclimatized to a greenhouse, grew normally and ultimately formed tubers in soil.