Basal stem cluster bud induction and efficient regeneration for the Tibetan endemic medicinal plant Swertia conaensis

Abstract

The artificial rapid propagation system for Swertia conaensis T. N. Ho et S. W. Liu was explored to screen the appropriate plant regeneration method and to provide an efficient propagation mode, useful for artificial breeding technology or for further research and development of the Tibetan endemic medicinal plant. In this study, the most suitable explant and hormone were chosen according to single factor test. Next, the effects of different hormone combinations on basal stem cluster bud induction, callus induction, adventitious bud occurrence and plant regeneration were investigated by using complete combination and orthogonal experiment. The obtained results showed that the explants suitable for in vitro of S. conaensis were stem tips with leaves, which were regenerated through the method of basal stem cluster bud occurrence in the MS medium with 2.0 mg∙L-1 6-BA, 0.5 mg∙L-1 NAA, but the proliferation coefficient was low, only 3.16 after 40 days of culture. Subsequently, the proliferation coefficient failed to improve, irrespective of change of the concentration ratio of 6-BA and NAA. Therefore, in the orthogonal experiment of adding ZT, the MS medium with 1.0 mg∙L-1 ZT, 0.5 mg∙L-1 NAA and 2.5 mg∙L-1 6-BA induced a large number of callus green and compact, with 86.30% callus occurrence rate. After 40 days of culture, the rate of adventitious bud occurrence was 96.55% and the proliferation coefficient was high (10.37). The rooting rate was 100% in the 1/2MS medium with 0.5 mg∙L-1 NAA. The survival rate of regenerated plants was more than 95%. Indirect organogenesis was more efficient than direct organogenesis in in vitro culture of S. conaensis. In this study, the efficient and stable regeneration system of S. conaensis was achieved through the method of explant to callus to adventitious buds, which provided an effective way to an endangered species.