AGROBACTERIUM-MEDIATED TRANSFORMATION OF HYBRID POPLAR SUSPENSION-CULTURES AND REGENERATION OF TRANSFORMED PLANTS

A1 method for Agrobacterium-mediated transformation of hybrid poplar ( Populus alba x P. grandidentata cv. 'Crandon') suspension cultures and regeneration of transformed plants is described. Transformants were r ecovered when suspension cultures were inoculated with Agrobacterium t umefaciens at a1 density of 107 colony-forming units ml-1, cocultivate d for 48 h, and plated to cellulose acetate filters on Woody Plant Med ium containing 4.5 muM 2,4-dichlorophenoxyacetic acid and 250 mg l-1 c efotaxime. Levels of cefotaxime greater than 250 mg l-1 were unnecessa ry for control of residual bacteria and inhibited callus growth. Trans genic plants were regenerated by culturing the transformed callus on m edia containing 0.11 to 27 muM thidiazuron. In contrast to thidiazuron , N6-benzyladenine had a1 negative effect on shoot regeneration; the c allus became necrotic when we attempted to induce shoots with concentr ations of 1. 1 to 8.9 muM, and growth was inhibited when concentration s of 0.11 or 0.22 muM were used to regenerate callus from suspension c ultures. Following cocultivation of poplar suspension cultures, we rec overed transgenic plants containing the maize transposon Ac, and callu s containing an insect toxin gene from Bacillus thuringiensis.