[Bt gene flow of transgeic cotton].
This study was carried out to determine the gene flow of transgenic cotton under Chinese ecological environment. Transgenic cotton GK-12 containing the marker gene NPTII and Bt gene was planted in the 6 x 6 m2 plot, non-transgenic cotton CCRC 12 and Xinmian 13 were planted respectively around them. At varying distances from transgenic cotton, seeds produced by the non-transgenic cotton were collected and screened for marker gene and Bt gene using kanamycine sulphate and Dot-ELISA method. PCR technique was also used in some seeds to screen Bt gene. The result indicated that gene flow was found to be high at 0-6 m, and to decrease with distances; however gene flow occurred up to distance of 36 m from the transgenic cotton plot. Bt gene flow at 3-6 m increased with increasing the diversity of transgenic cotton in the plot, but gene flow increased little at long distance. The gene flow between species was lower than between cultivars at 0-6 m, and occurred at the distance of 72 m from transgenic plot. 72 m buffer zones would serve to limit gene flow of transgenic cotton from small-scale field test. The possibility of escapes of engineered gene to wild relatives of cotton species was also discussed.