[Objective] This study aimed to investigate the frequency of exogenous gene flow to non-transgenic conventional rice cultivars and assess the potential risks of marker-free of insect-resistant transgenic rice to agricultural ecological environment. [Method] Insect-resistant transgenic rice variety HUAHUI No.1 was planted as the experimental material and surrounded by several non-transgenic conventional rice cultivars. F1 non-transgenic rice seeds were collected according to different distances and identified by using PCR technology, the frequency of exogenous gene flow from insect-resistant transgenic rice to non-transgenic conventional rice cultivars was counted and analyzed. [Result] The average frequency of exogenous Bt gene flow to P13381 and CHUNJIANG063 was 0. Transgene flow occurred to varying degrees from insect-resistant transgenic rice HUAHUI No.1 to several non-transgenic rice lines including HEX122-2, TIANXlANG, MINGHUI63 and Pl157, with the maximum average gene flow frequency of 0.875%. The frequency of gene flow was gradually reduced with the increase of distance, and the average transgene flow frequency de- creased to 0 in all the sampling points 7 m away from transgenic rice material. [Conclusion] This study revealed that the exogenous gene flow frequency of insect-re- sistant transgenic rice variety HUAHUI No.1 was very low, leading to very small risk to the eco-environment. Rational distribution in the field for physical isolation, keeping the appropriate distance and scientific farming arrangement to avoid the synchronization of flowering can effectively control the exogenous gene flow from transgenic rice and reduce he ecological risks caused by transgene escape.
