PLANT-REGENERATION FROM LEAF TISSUES OF SIBERIAN ELM

Plants were regenerated from leaf tissue of greenhouse-grown seedlings of Siberian elm (Ulmus pumila L.). Shoot regeneration was induced on Murashige and Skoog (MS) medium containing 5 to 10 mu M of BA. Up to 5 5% of the leaf explants formed shoots with an average of 2.4 shoots pe r explant. Addition of 2.5 or 5 mu M of IBA failed to enhance regenera tion. Thidiazuron at 0.5 or 1.0 mu M also induced shoot regeneration, but the shoots failed to elongate as well as shoots regenerated from m edia containing BA. Incubation in darkness for 7, 14, or 21 d had litt le effect in promoting shoot regeneration, except that incubation for 21 d increased shoot regeneration on the medium with 5.0 mu M BA. Geno types differed in shoot regeneration potential, with regeneration freq uencies ranging from 13% to 55%. Regenerated shoots were micropropagat ed on Driver and Kuniyuki Walnut medium. Ninety percent of microcuttin gs rooted directly in potting soil. This regeneration system will be v aluable for genetic transformation and cell selection of Siberian elm. Chemical names used: 6-benzylaminopurine (BA); indole-3-butyric acid (IBA); N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron, TDZ).