Abstract:

In order to achieve precociously flowering of poplar and shorten the genetic and breeding period, we studied factors affecting genetic transformation of FT 1 gene controlled by Heat Shock Promoter in hybrid aspen clone (Populus tremula×P. tremuloides) and optimized the Agrobacterium-mediated transformation conditions. FT 1 gene was transformed into hybrid aspen through optimized transformation protocol and the 2-3 months transgenic plants were successfully induced to precociously flower by heat shock. The results showed that regeneration frequency of kanamycin resistant plants of hybrid aspen were significantly affected by pre-culture of leaf disc, Agrobacterium concentration, incubation duration,and co-culture duration. Optimized transformation protocol was as follows: leaf discs were pre-cultured for 6 days on the callus-induction medium, incubated for 60 minutes in Agrobacterium solution to reach to the OD₆₀₀ value of 0.5, and then co-cultured for 2 days. According to this protocol, regeneration frequency of kanamycin resistant plants can reach to 29.84%. Expression of FT 1 and precociously flowering of transgenic plants were induced by heat shock treatment of 37 ℃, 1 hour per day for 3 weeks. The size of transgenic plants was a limiting factor that affected the precociously flowering induced by heat shock, and plants with height less than 20 cm didn't show precociously flowering when induced by heat shock. Heat shock can induce more normal flowers, but extensive aberrance was still presented.

Key words: FT gene, heat shock promoter(HSP), Populus, genetic transformation, precociously flowering