Molecular Marker Assisted Selection For Improving Japonica Resistance To Rice Stripe Disease

Rice stripe disease is caused by rice stripe virus which is transmitted by the small brown planthopper. Recent years, rice stripe disease occurred seriously in Jiangsu, Zhejiang etc, and it has caused a great loss of rice production. So the most important breed object is to improve the rice resistance to rice stripe disease and breed new varieties which have resistance to rice stripe disease. With the development of molecular marker technique and deep study of rice stripe disease, molecular marker-assisted selection (MAS) for the anti-rice stripe disease genes is possible.In this study, the resistant indica wide compatibility variety Dular and japonica variety Kuifeng were used as the donors, while Wuyujing3, Wuyunjing7 and Wuyunjing8 were the receptors. In order to improve receptors'resistance to rice stripe disease and breed new varieties which have resistance to rice stripe disease, the anti-rice stripe disease genes called qSTV-11b and qSTV-11c on chromosome 11 were introgressed from donors to receptors by molecular marker-assisted selection. Main results are as following:1.Until2007, 917 plants contain two anti-rice stripe disease genes were selected from BC₄F₁ population and account for 23.99 percent of the total plants detected in BC₄F₁ population. 603 plants contain homozygous resistant genes were selected from BC3F2 population and accounted for 18.25 percent of the total plants detected in BC3F2 population.2. We identified the resistance to rice stripe disease of BC₂F₃ lines which contain homozygous resistant genes. The resistance level of 18 BC₂F₃ lines whose receptors areWuyujing 3 belongs to resistance. Among 46 BC₂F₃ lines whose receptors were are Wuyunjing 8, 36 BC₂F₃ lines have the resistance, and 10 BC₂F₃ lines lost the resistance or their resistance level belongs to moderately resistant. The resistance level of two receptors belongs to high susceptible. The results indicated that the anti-rice stripe disease genes introgressed into receptors by backcross with the help of molecular marker-assisted selection can improve the resistance of the receptors obviously.3. According to plant height, 1000-grain weight and grain number per culm of the plants contain anti-rice stripe disease genes inBC3F2 and BC₄F₁ population, we made a nonhiearchical clustering in order to select plants the same as the receptors. 10 plants contain homozygous resistant genes and 32 plants contain heterozygous resistant genes were selected. These 42 plants are all the same as Wuyujing3. 5 plants contain homozygous resistant genes and 19 plants contain heterozygous resistant genes were selected. These 24 plants are all the same as Wuyunjing8. 9 plants contain homozygous resistant genes and 16 plants contain heterozygous resistant genes were selected. These 25 plants are all the same as Wuyunjing7.4. According to separation conditions and comprehensive characters of each BC₂F₃ line, 14 BC₂F₃ lines which have excellent characters were selected. Among these 14 BC₂F₃ lines, single plant yield of 5 BC₂F₃ lines whose receptors were Wuyujing 3 is higher than the single plant yield of Wuyujing3and the range of increasing in yield was 20.58%-58.62%. Among 9 BC₂F₃ lines whose receptors were Wuyunjing 8, there were 4 BC₂F₃ lines whose single plant yield over Wuyunjing 8 and the range of increasing in yield was 3.10%-13.84%. Among these 14 BC₂F₃ lines, there were 4lines whose appearance quality reach the standard of national third high quality rice.