Fitness Of Hybrids Between Bar Gene-containing Transgenic Rice And Common Wild Rice Under Natural Conditions In Hainan

In recent years, along with the rapid development of genetically modified rice, China has access to a number of fine varieties of rice by transgenic technology, such as insect resistance, disease resistance, stress tolerance, herbicide-resistant traits. In which bar gene-containing transgenic rice with herbicide resistance shows very attractive application prospects. Nevertheless there are lots of studies have shown that the bar transgenic rice pollen flow to the common wild rice populations inevitably. Common wild rice is an important gene pool which contains a large number of elite genes. In order to assess the environmental consequences caused by transgene escape, we analyzed the fitness of bar transgenic rice with 3 common wild rice hybrids and potential impact to common wild rice populations. The results could deepen our understanding of the environmental impact of bar transgenic rice and provide a reference for the protection of the populations of common wild rice.Fitness is defined in terms of a range of individual survivals and successful reproductive opportunities. The higher of fitness, the greater the chance of individual survival and the success reproductive opportunity. Fitness of transgenic rice and common wild rice hybrids decide whether they can survive in common wild rice populations. The F1 hybrids of bar transgenic rice B2 with common wild rice (abbreviated as "Bar-wild hybrids") were obtained through artificial hybridization, in which B2 were used as the male parent while common wild rice were used as the female parent respectively. Furthermore we investigated the resistant obtaining rate, the germination rate, agronomic traits competitiveness and survival rates in common wild rice populations of hybrids. The results are as follows:The hybridization between bar transgenic rice B2 and all common wild rice was accessible. The seed setting rate and resistance obtained rate (calculate in terms of gene flow frequency) of hybrids were 5.6% and 24.8%, respectively. But the resistance obtained rates had different values which varied from 7.7% to 95.5%. The hybrids of F1 had better agronomic traits for a higher germination rate than the corresponding common wild rice seeds in the early stage, but they had weaker weed suppression of weed, and were the weak competitor against the weeds. The wild rice populations have good overwintering ability for their creeping growth and vegetative reproduction in wild conditions. The numbers of F1 plants were decreasing in common wild rice populations.The common wild rice had better performance than F1 hybrids in rice stubble ratooning. The rate of stubble ratooning of F1 hybrids is up to 144% after three seasons, while common wild rice is up to 256%(the number of stubble regeneration were more than rice stubbles). The stubble ratooning of F1 plants were not better than the common wild rice in space preemption and suppression of weed. The seeds germinate rate of F2 and F3 hybrids were less than 2% in the harsh growing conditions of common wild rice populations.In summary, although the germination rate, the agronomic traits, growth competitiveness of F1 plants had better performance than common wild rice, but due to the ratooning and creeping growth of common wild rice, the F1 hybrids plants was still vulnerable in common wild rice populations. Additionally, the quantity of the hybrids plants in common wild rice populations reduced along with the generation increased, it indicated that the F1 hybrids of bar transgenic rice with common wild rice did not display higher fitness. Therefore, we conclude that gene flow of bar transgenic rice B2 would not impact the common wild rice populations after several seasons.