AGROBACTERIUM-MEDIATED TRANSFORMATION OF QUAKING ASPEN (POPULUS TREMULOIDES) AND REGENERATION OF TRANSGENIC PLANTS

Agrobacterium-mediated gene transformation of Populus tremuloides Mich x was accomplished by co-cultivation of leaf disks excised from greenh ouse plants with Agrobacterium tumefaciens containing a binary Ti-plas mid vector harboring chimeric neomycin phosphotransferase (NPT II) and beta-glucuronidase (GUS) genes. Shoot regeneration in the presence of kanamycin was achieved when thidiazuron (TDZ)was used as a plant grow th regulator. Transformation was verified by amplification of NPT II a nd GUS gene fragments from genomic DNA of transgenic plants with polym erase chain reaction (PCR) and integration of these genes into nuclear genome of transgenic plants was confirmed by genomic Southern hybridi zation analysis. Histochemical assay revealed the expression of GUS ge ne in leaf, stem and root tissues of transgenic plants, further confir ming the integration and expression of T-DNA in these plants. This pro tocol allows effective transformation and regeneration of quaking aspe n using greenhouse-grown materials as an explant source. Whole plant r egeneration from cuttings of field-grown mature quaking aspen and hybr id poplar (P. alba x P. grandidentata) was also readily achieved by us ing this protocol, which represents a potential system for producing t ransgenic quaking aspen and hybrid poplar of valuable genotypes.