Study On The Containment Of The Transgenic Rice Gene Flow By Using Different Physical Barriers

In rice production, distance isolation and flowering time isolation were two common methods to control the transgenic rice gene flow, and barrier isolation was used in small area of seed reproduction and rice hybrid breeding. Up to date, most of rules of different settings for isolation were obtained from long-term experience. Facilitated by the development of the genetically modified crops and their application, setting rules like distance, frequency and their effect on gene flow could be deeply studied with transgenic makers. As a feasible method physical barrier was widely used, while its efficacy on rice transgenic gene flow contrql was not determined till now. Take the advantage of anemophilous characters of rice flowers, jointed with check out protocol of trans-bar-gene rice plant in the laboratory and in the field, we have studied the effects of principles of physical barriers and different pollen donors on gene flow. This research can provide the basis for the application and assessment of isolation methods on commercial production of transgenic rice. Meanwhile, rice seed production and breeding of transgenic rice could also benefit from this.Taking transgenic rice B2as pollen donor, the conventional rice Texianzhan25and male sterile line BoA as the pollen recipients, parallel experimentations on effect of barriers for Transgene flow were designed independently. The results could be summarized as follows:(1) Seedlings were categorized into two groups under herbicide Basta, normal green seedlings and (withered seedlings. Most seedlings of texianzhan25on F1generation were withered, and the number of left green seedlings decreased while distance increased. And, the number of green seedlings of BoA on F1generation reduced while distance increased, showing the same tendency with the previous one.(2) All the green seedlings resistant to Basta contained bar gene fragment, no pseudo-positive seedlings were founded.(3) The frequencies of both germplasms of Transgene flow (shorted for ’FTF’as follow) reduced as distance increasing, they decline rapidly at short distance while gently at long distance. The FTF of line BoA was significantly higher than that of Texianzhan25.(4) The FTF was greatest when only BoA existing as the recipient and the pollen donor was surrounded with2m high isolation cloth, and its value was from21.612%to35.396%within10m. It was significantly higher than other treatments. The values of other treatments:no measures to the pollen donor, isolation cloth surrounding with no division inside and with division inside were from5.683%to17.708%,3.831%to9.116%and1.133%to4.850%respectively. The FTF of maize barrier treatment within20m was from0.434%to2.665%.(5) To the conventional rice Texianzhan25, FTF of treatments no measures to the pollen donor, isolation cloth surrounding with no division inside and isolation cloth surrounding with division inside were from0.021%to0.164%,0.011%to0.125%and0.006%to0.072%respectively. The FTF of maize barrier treatment within20m was from0to0.022%at the same situation.(6) The results of parallel experimentation within two seasons were affected by weather conditions, such as temperature, humidity and wind, but the tendency of efficacy of planting long-stalked crop like maize, isolation cloth surrounding with division inside, isolation cloth surrounding with no division inside and no measures to the pollen donor, was decreased gradually. However, Transgene flow was inevitable even if using all the above measures to isolating pollen flow.The FTF were different when pollen donors changed. In the following studies, Indica transgenic rice B9and Japonica transgenic rice B2were chosen to be pollen donors, Texianzhan25and BoA were taken as pollen recipients. Results showed that the FTF was still reduced as distance increased, and the FTF to the BoA lines was significantly higher than the conventional rice cultivars Texianzhan25. When the ms line was taken as the recipient, the FTF of B2was from3.906%to45.934%, which was higher than B9(from1.325%to23.948%) at any distance. However, taking Texianzhan25as the recipient, the result was opposite at the distance of the first6m, and interactions were showed after6m. The FTF of B2was from0.041%to0.435%, it was from0.015%to1.189%forB9.In short, the FTF varied from different pollen donors or recipients. Transgene flow would be weakened but not absolutely impeded from pollen flow by physical barriers.