A Study On The Variation Of RolB Transformed Clones Of Populus Tomentosa

Populus tomentosa is an important tree species in China, with the excellent characters of fast-growing, long-life and nice quality of wood. It is widely planted in the north of China for wood industry. However, it is difficult to root from wood cuttings which reduce its value in industry. In order to improve the rooting ability of the Populus tomentosa, the rolB gene was transformed into the plant and the transgenic clones were obtained. In this work, the transgenic plants were studied through rooting experiments, hardwood cutting experiments, determination of endogenous hormone and variation in growth. The main research work and the results are as follows:1. The clones of the transgenic plants were identified by PCR, and the positive clones were obtained.2. The in vitro rooting results showed that the transgenic clones rooted from 80% to 100% without auxin, while only 13%~20% for the control plants. Transgenic plants showed the high sensitivity to the auxin. When the concentration of IBA reached 1.0 mg/L, the rooting of the transgenic clones were restrained.3. In the experiment of hardwood cutting without any auxin treatments, both the first and the second cuttings of the rolB transformed plants had a significantly higher rooting ability than the cuttings from the untransformed plants. The rooting percentage of the first cutting from transgenic plants was 75.8%, and the second cutting was 75.8%, while only 56.7% and 36.7% for the controls. The second cutting of the rolB plants had significantly higher rooting ability than the first cuttings, while it is contrary to the control. It is proved that the rolB gene had a higher expression in the region close to the root. In the experiment of hardwood cutting treated by auxin, the cuttings of the rolB transformed plants increased sensitivity to auxin. When the concentration of IBA reached 2000mg/kg, the rooting of the transgenic clones was restrained.4. The endogenous hormone of the transgenic plants was determined by GC-MS-SIM. The change of hormone in the rolB plants is similar to the controls in the different period of cutting experiment. In the time of rooting, the cutting of rolB plant showed higher endogenous IAA contents and lower ABA contents than the controls. The expression of the rolB gene was correlated with endogenous hormone and the rooting capacity.5. Growth analysis showed that the stem height of the transgenic clones was lower than the controls in the first year of transplants. The dwarfism appeared in the transgenic plants. The transgenic clones showed a similar physiological index to the untransformed control plants. In the second year of transplant, the dwarfism of transgenic plants was reduced, and grew as well as the controls.