Shoot organogenesis from leaf explants of Dayaoshania cotinifolia W. T. Wang.

Dayaoshania cotinifolia W. T. Wang is a rare and endangered member of the Gesneriaceae family which is endemic to China. To conserve this species, an efficient in vitro propagation and regeneration system via shoot organogenesis was established from young leaf explants. Adventitious shoot induction was possible within 50-60 d on basal Murashige and Skoog medium supplemented with 1-3 μM 6-benzyladenine, although 5 μM 6-benzyladenine induced hyperhydricity. Basal medium containing 1-5 μM thidiazuron induced fewer shoots, while 1-5 μM α-naphthaleneacetic acid induced numerous adventitious roots and a few adventitious shoots. However, when thidiazuron and α-naphthaleneacetic acid were combined, both the induction percentage and number of shoots increased. Leaf explants cultured on induction medium supplemented with 1-5 μM 2,4-dichlorophenoxyacetic acid become necrotic and died. Induction medium supplemented with 1 μM α-naphthaleneacetic acid and 1-3 μM 6-benzyladenine was optimal for inducing adventitious shoots as was the combination of 1-3 μM thidiazuron and 1 μM α-naphthaleneacetic acid. Induction medium containing 2.0 μM 6-benzyladenine and 0.5 μM indole-3-acetic acid was optimal for the multiplication of adventitious shoots. Rooting was achieved on half-strength MS medium supplemented with 3.0 μM indole-3-acetic acid or α-naphthaleneacetic acid and 0.1% activated charcoal. Plantlets were transplanted to a mixture of sand, vermiculite, and humus (1:1:1); 92% survived. This protocol is a unique and effective means to micropropagate this rare and important plant and could serve as a solution for in vitro and ex vitro conservation. [ABSTRACT FROM AUTHOR]