On Safety Assessment Of Gene Flow Of Transgenic Herbicide-resistant Crops By Sexual Compatibility Of Plant

The concominant weeds and relatives with different level (near and far comparatively) of relatedness from transgenic herbicide-resistant crops were selected as experimental materials based on the principle of time relation, space relation and quantity relation of those related population. By means of reproductive biology plus hand-pollination and open-pollination, the assessment methods and techniques of gene flow from transgenic herbicide-resistant crops to different relatives were studied based on the sexual compatibility which is the first important condition of gene flow. Especially the fast test method for these species which incompatibility occurred at early stage of pollen germination was provided by this experiment. Meanwhile the possibilities of gene flow from transgenic herbicide-resistant rice (Oryza sativd) and oilseed rape (Brassica napus)io their relative species were assessed. The fast test techniques and methods for assessment on the gene flow of transgenic herbicide-resistant crops were provided. And the assessment measure of different level to different relatives was put forward firstly.1. Gene flow of transgenic herbicide-resistant rice1.1 The biology of anthesis of Echinochloa spp. was studied and reported firstly. The daily anthesis rhythm was 77-80% before 7:00, 15-20 % during 7:00-8:30, sporadic after 8:30, and no anthesis was obseved after 10:30. This showed the flowering time didn't overlapped between Echinochloa spp. and rice due to 9:00-10:30's rice anthesis, which the possibility of gene exchange may be low. The pollen vitality of E. crusgalli var. mitis collecting directly from spikes decreased slowly. At 3h after anthesis, the pollen vitality was still 17.31%. This showed the pollen ofE. crusgalli var. mitis could keep vitality until rice was blooming. The possibility of potential gene flow could still exist between transgenic herbicide-resistant rice and E. crusgalli var. mitis .1.2 The fact that the sexual incompatibility between transgenic rice and Echinochloa crusgalli var. mitis occurred at the stigma was observed with light-microscope firstly bymeans of reproductive biology. The sexual incompatibility lie in the fact that pollen grains of transgenic rice on the stigmas of barnyard grass couldn't germinate nor grow normally after cross, and couldn't penetrate the stigmas of barnyard grass. Moreover the sexual incompatibility couldn't be broken under the mentor pollen inducement. Furthermore the fact that emasculated barnyard grass pollinated with the rice pollen grains couldn't seed and produce no hybrid in field supported the incompatibility between them. Therefore, the possibility of gene flow between them was relatively low. The fast test method for these species which incompatibility occurred at early stage of pollen germination was developed from this experiment.1.3 The gene flow of pollen cross between wild rice (O. offidnalis ) and two varieties of transgenic rice with bar-gene was studied by means of reproductive biology. The results showed that the pollen grains of two varieties of transgenic rice could germinate on the stigmas of wild rice and their pollen tubes could grow and penetrate stigmas of wild rice normally, but the percent of pollen grains penetrated wild rice stigmas or condensed and released pollen inclusions after cross was lower than that of self-pollination. The fact that the emasculated wild rice pollinated with transgenic rice pollen grains couldn't seed showed they were sexual incompatibility. However the probability of horizontal gene transfer could be increased because the pollen grains of rice could germinate and grow on the stigmas of wild rice and released the inclusions. Under this experiment condition, gene flow between wild rice and transgenic rice with bar-gene didn't occur successfully. The optical microscope was not suitable for the observation of the sexual incompatibility after stigma.1.4 The possibility of gene flow between transgenic rice and weedy rice(0. saliva) was assessed by the results of the germina...