Abstract: The leaf disc method developed by Horsch et al. (1985) has been used for transformation of Populus tomentosa. The strain of Agrobacterium tumefaciens used harbored a reconstructed Ti plasmid which contained gene 4 of T–DNA and the chimeric CAT(chloramphenicol acetyltransferase) gene. Leaf explants from shoot cultures of Populus tomentosa were co-culfivated with the bacterium. On the hormone free medium, teratoma-like shoots developed from the edge of the leaf explants. When the abnormal shoots were excised from the explants and transferred onto rooting medium, a mass of callus formed at the base of shoots, with new shoots developing, but without root formation. The measurement of'endogenous cytokinin showed that the transformed shoots produced 14 times as much iso-pentenyl adenosine as untransformed shoots did. All teratoma-like shoots-tested showed the presence of nopaline, and were able to grow well. on the medium containing 60-100μg/ml chloromycetin, while normal shoots turned white after 40 days. Pretreatment of A. tumefaciens with phenolic compound, salicylic acid, would increase the frequency of transformation significantly.

Key words: Populus tomentosa, Agrohacterium tumefaciens, Transformation