Inheritance And Fine Mapping Of Resistance Gene To Soybean Mosaic Virus Strain In Soybean

Soybean mosaic virus disease, caused by soybean mosaic virus （SMV）, is one of the most broadly distributed viral diseases worldwide in soybean. It causes yield loss and seed quality deficiency seriously. Breeding resistant varieties is the most economical and environment-friendly method for controlling this disease.The keys of breeding resistant varieties depend on resistant resources, molecular mapping of resistance genes and the realization of inheritance mechanisms of resistance to SMV.SMV has been classified into21strains based on the reactions of SMV isolates on a set of soybean differentials in China. SC6and SC17are SMV prevalent strains of Huang-Huai-Hai valleys and the north spring soyean production respectively. In order to lay a foundation for molecular marker-assisted selection in breeding programs and cloning of resistant gene. The purposes of this study were to identify resistance resources to SC6and SC17, determine the inheritance of resistance reactions to SC6and SC17, and fine map the resistance genes.1. Identification of resistant resourcesThe study has evaluated the new breeded279soybean cultivars, which participated in the2009-2010regional soybean tests nationwide. The results showed that19cultivars such as Zhongdou35, Q0926are anti-infection to SC6and SC17, accounting for6.81%of the total. In the279soybean cultivars, there are52cultivars performing quantitative resistance to SC6, accounting for18.64%, and50cultivars performing quantitative resistance to SC17, accounting for17.92%. These cultivars above not only can be used in production directly, but also can breed resistance cultivars to SMV as a kind of germplasm resources. In these cultivars, there are73High Resistance （HR） and Resistance （R） cultivars to SC6, accounting for26.16%, and75to SC17, accounting for26.88%. The others belong to the middle type: Moderate Resistance （MR） and Moderate Susceptibility （MS）, occupied the main part. The results also showed that the cultivars from the north of China are relatively better in resistance, such as Liaoning, Shanxi and Hebei provinces, the average disease index of these provinces are under30below, However, the average disease index of Fujian, Jiangsu and Anhui provinces are more than30comparatively.2. Analysis of inheritance, fine mapping and evaluate to resistant genePopulation were created between resistant （R） and susceptible （S） parents or R and R parents. F1, F2and F2:3were derived from selfed inbred.The parents and populations were used to determine the inheritance for resistance to SMV strain SC6and SC17. The results showed that1:DouguanNo.1, Ke9302, Qihuang22and Q0926contain a single dominant resistant gene to SC6strain,2:QihuangNo.1, JiDoul8, Ke9302, JinDoul9and Zhongdou35contain a single dominant resistant gene to SC17strain,3:the resistance genes to SC6in QihuangNo.l and Kanggyo are alleles or very closely linked4:the resistance genes to SC17in Zhongzuo045323and Ke9302may were not at the same locus.The new developped SSR marks were used for fine mapping Rsc6in Q0926and Rsc17in Zhongdou35.Finally Rsc6was located on chromosome2with a distance of0.775cM from BARCSOYSSR₀2₀617and0.519cM from BARCSOYSSR₀2₀621on the other side, and RSC17was also located on chromosome2with a distance of0.264cM from BARCSOYSSR₀2₀622and0.262cM from BARCSOYSSR₀2₀627on the other side.Rsce and Rsc17were evaluated with ten strains/isolations, the results indicated that Q0926has better agronomic trait than KefengNO.1, QihuangNO.1and PI96983in resistance and other aspects. No symptom can be caused by ten strains/isolations on Q0926. Meanwhile, only three strains/isolations can induce mild mosaic symptom on Zhongdou35.3. The relationship of necrotic gene with Rsv genePI96983, Dabaima and Jinda74inoculated with SC6strain were respectively cultivated at25/28℃and32/35℃.The results indicated that temperature and necrosis gene expression is closely related, and necrosis gene expression can be easily induced under the former condition.In aaddition, the necrosis gene in Jinda74can be expressed completely at25/28℃. F2population derived from Jinda74（N） xNannong1138-2（S） inoculated with SC6. Inheritance analysis were conducted and checked by x2test.The results showed that when the necrosis gene was expressed completely, the F2population fit a3（N+MN）:1（M+R） ratio. F1were all necrosis. All this results indicated that necrosis sympton is controlled by a single dominant gene.