| Rice stripe disease (RSD) is a viral disease transmitted by the small brown planthopper (Laodelphax striatellus Fallen). It’s one of the most important diseases which seriously affected the yield of japonica in Middle-Lower Yangtze Area in recent10years. Chemical prevention and control has little effect to the disease. So, improvement of rice stripe disease resistance for rice cultivar is considered to be the most economical and effective way. Wuyunjing7is a high yield variety in Jiangsu province. Because this cultivar has so many advantages such as has high yield, strong resistance and wide adaptation, it was approved by the Jiangsu, Shanghai and National Crops Variety Approval Committee from1998to2000and became the main cultivar of single-cropping late japonica rice variety at Jiangsu province, Shanghai, Zhejiang province and Anhui province in the late1990s. According to incomplete statistics, Wuyunjing7had cumulative extension area more than1.2million hm2from1997to1999, and it was the conventional japonica variety, which had the most extension area at that time. At the same time, this cultivar was also the pioneer of conventional japonica which had700kg yield in the production. Since2000, rice stripe disease happened continuously and seriously. Wuyunjing7was highly susceptible to this disease, and it limited the further application of Wuyunjing7. In this situation, this variety still had an extension area about40thousand hm2at present. So, improvement of rice stripe disease resistance for high yield variety Wuyunjing7is very important for extending its service life in production and developing new rice germplasm resource for resistance to rice stripe disease. In this study, we used high quality japonica Kantou194as the donor parent of resistance gene Stv-bi,to improve the RSV resistance for high yield and susceptible variety Wuyunjing No.7with the breeding strategy of directional backcross. In continuous backcross and selfcross generations, the marker tightly linked with Stv-bi was used for molecular marker assisted selection (MAS), by combining with the identifications of field resistance to RSV and agronomic traits analysis. Finally,14improved rice lines carrying the disease-resistance gene were obtained. On the basis of this study, the agronomic traits and quality traits for14 improved rice lines of Wuyunjing7to stripe disease were analyzed with line comparative test method, and then, the best one in14lines was chose. The main results are followings:1.14improved rice lines of Wuyunjing7to stripe disease were achieved by marker assisted selection and field selection. Determination of the genotype of individuals from the14improved rice lines show that all of the14improved rice lines have resistance gene Stv-bi,and they are homozygous genotype. The incidence of rice stripe disease for14improved rice lines was proved to be lower than Wuyunjing7and Wu-yu-jing No.3by using the method of field resistant test. It shows that the resistant of the14improved rice lines has been improved obviously.2. The yield, agronomic traits and quality traits for14improved rice lines were analyzed with line comparative test method. The result shows that most agronomic traits and quality traits of the14improved rice lines have no significant difference with Wuyunjing7besides neck length of spike and primary branch which are easy to be interfered by environment. The yield of the improved lines is similar to Wuyunjing7too. The yield and quality traits of some improved lines are even better than Wuyunjing7.3. The excellent lines such as C06, C07and C14were selected by comprehensive performance. These lines are not only better than other lines in the resistance of rice stripe disease, but also similar to Wuyunjing7in yield, the agronomic traits and quality traits. |
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