Research On Ecosystem Safety Evaluation Of Transgenic Poplar

The progressive genetic engineering provides a promising tool to tree breeding. The researches of transgenic trees have come out from laboratory to field test, environment release and commercial application. In China, transgenic poplar expressing Bacillus thuringiensis toxin gene (Bt) have been applied in the plantation for pest control, and the plantation is about 250 hectares. At the same time, the ecosystem problem of transgenic poplar come in for general attention, in that the most important is about transgenic poplar gene flow. Because of the dominated asexual reproduction in poplar trees, research on poplar pollen spread is relatively less. In foreign countries transgenic trees must be cut down before flowering, so the research on gene flow of transgenic trees is relatively lagging. In this article the research is mainly on the genetic stability of Bt gene and hybridization compatibility of transgenic poplar with other poplar species, flowering synchrony of transgenic poplar and it's dose related congener, pollen dispersal and it's influencing factors of transgenic poplar, and reproduction and regeneration of transgenic poplar natural hybrid progeny. And ecosystem risk of transgenic poplar is assessed. The mainly contents are as follows:By using PCR test of transgenic poplar plant and the hybrid to confirm Bt gene stability and hybridization compatibility with it's related congener, to offer proof of assessing gene flow. In this research, the result of analyzing 14 clones of transgenic poplar lines indicates that after 12 years field test the Bt gene is stable in the genome of the poplar. On this base, one randomly selected line is used to do genetic analysis. In the selected strain 172(♀), Bt gene is dominant and can transfer to its progeny and the segregation of progenies is conform to Mendel's law. After artificial crossbreeding poplar(♀) with transgenic poplar 197 (♂) and Populus pioneer (♀) with transgenic poplar 197 (♂), result of PCR test on the progenies explain that transgenic poplar has high hybridization compatibility with general poplar and Populus pioneer and the Bt gene can stably transmit to the progenies. Investigation of flowering phenology explain that transgenic poplar and Populus pioneer poplar have the same five-day flowering period. According to the above results, it is possible for the gene flow of Bt gene to escape into the environment.Pollen spread is the main method of transgenic plant gene flow. In this research poplar pollen PCR test is the research method to analyse the transgenic poplar spread and influencing factors. Transgenic poplar gene flow is assessed through the pollen spread. The result about pollen spread was as followed:(1)Transgenic poplar pollen spread probability was 1.642‰, 0.485‰, 0.33‰at the distance of Ore, 200m, 50Om respectively, at 800m no transgenic seed was found. The pollen spread probability was decreased as the distance increased between the transgenic poplar and Populus pioneer.(2)Generally, the poplar pollen dispersal was about 1km. In this study, SE3 (800m) was found no filial generation of transgenic poplar. The reason could be the big non-transgenic colony (1000), the number of transgenic poplar was too small(22), transgenic pollen didn't reach, or the probability was too low to be tested.(3)Wind direction and wind speed were main factors. Sample was collected at the northeast and southeast of Populus pioneer. At the southeast 500m distance filial generation of transgenic poplar was tested with the probability of 0.33‰, at the northeast the nearest distance. 386m no filial generation of transgenic poplar was tested.Propagation and survival of transgenic plant progenies is an important step for the foreign gene of transgenic plants to escape into the environment successfully. In order to know survival and natural regeneration of transgenic poplar progenies, the transgenic seed vigor under different storage condition and their germination and seedlings survival in the field are studied. The results show that the germination of the seeds under field conditions without direct sunlight decreased to 12%, the sprout of transgenic poplar seeds is very short under the natural condition. During the experiment of the transgenic poplar seeds propagation in the field, the germination of the seeds is zero, and the survival of seedlings is 6.1% with watering, site preparation and weed management. It is concluded that the regeneration of the transgenic poplar under natural condition is very difficult.Therefore, although the stable inheritance of Bt gene, the hybridization compatibility with relatives and flowering synchrony and the effective dispersal within 500m distance, it is impossible for the transgenic poplar to escape into environment under the natural condition in the drought area of north China, and the ecologic risk of the transgenic poplar will not happen.