Efficient tissue culture and Agrobacterium-mediated transformation of haploid poplar derived from anthers

Calli were induced from anthers of Populus simonii x P. nigra. Haploid plants were then regenerated from the callus and multiplied efficiently by culturing leaf explants. The presence of both haploid and diploid cells in the same plant revealed spontaneous chromosome doubling in haploid cells. The haploid plants were transformed with the nptII gene by Agrobacterium-mediated method using leaf explants, and five independent kanamycin-resistant lines were obtained, with a transformation frequency more than 6%. Further PCR test indicated that the exogenous betA gene was transferred into these kanamycin-resistant lines, which were still haploid. Thus, the efficient tissue culture system and transformation of haploid poplar plants were achieved. Our study will contribute to forest improvement via the haploid culture and transgenic technology.