Abstract:Cowpea trypsin inhibitor (CpTI) gene, an insecticidal gene, was introduced into poplar ( Populus tomentosa Carr. ) by gene transformation mediated by Agrobacterium tumefac/ens (Smith et Townsend) Conn. The influences on regeneration and transformation frequency of poplar by the concentration and addition of kanamycin were compared. Kanamycin resistant (Kmr) plantlets were obtained by 3 -4 cycles screening in selective condition. The ability of leaf regeneration and shoot subculture and rooting from the transformed and non-transformed plants in the presence of 50 mg/L kanamycin was examined. The presence of CpTI gene in the transgenic plants were confirmed by PCR and PCR-Southern blot. Assay on proteinase inhibition activity demonstrated that leaf protein extracts of the transgenic poplar showed higher inhibition activity against trypsin than that of control plants.