Callus induction and frond regeneration in Spirodela polyrhiza

Spirodela polyrhiza belongs to the family Lemnaceae (duckweed), which is a group of small aquatic plants offering an attractive plant expression system for the production of recombinant protein. No frond regeneration protocol has been established in this species yet. An efficient protocol for plant regeneration through organogenesis has been developed in Spirodela polyrhiza for the first time. Calli were successfully induced from 92% of explants on Murashige and Skoog (MS) medium with 10 mu M naphthaleneacetic acid, 2 mu M thidiazuron, 1 mu M 2,4-dichlorophenoxyacetic acid (2,4-D) and 3% sucrose. MS medium containing 1% (m/v) sorbitol and 1 mu M 2,4-D supported long lasting growth (at least 5 months) of 98% of calli. Plants regenerated from 92% of calli on Schenk and Hildebrandt (SH) medium with 10 mu M zeatin and 1% (m/v) sucrose. The protocol for frond regeneration could be a good basis for transgenic engineering of S. polyrhiza.