Fine Mapping Of SC18 Resistance Gene To Soybean Mosaic Virus

Soybean is one of the important grains and oil crops in China because of its rich oil and vegetable protein that is easily absorbed by human body.However,soybeans are susceptible to pests and diseases,and Soybean Mosaic Virus（SMV）is a widespread soybean disease in the world which has a serious influence on the yield and quality of soybean.Soybean mosaic virus SC18 is a dominant strain widely distributed in southern soybean producing areas,but the genetic mechanism of its resistance is not fully clear.Therefore,it is available to prevent and control the prevalence of SC18 in southern soybean-producing areas of China.The main purpose of this study was to identify the symptoms and genetic patterns of resistance genes of SC18 strains using Recombinant Inbred Lines（RILs,Zhonghuang24×Huaxia3）,the progeny of segregated populations F₁derived from Zhonghuang24×Huaxia3,F₂ and other soybean varieties（lines）.The high-density genetic map was used to map the resistance genes of SC18 strains of Zhonghuang24,providing a theoretical basis for molecular disease resistance breeding and gene function verification.The results are as follows:A total of 71 cultivars were inoculated with SC18 strain,including soybean varieties（lines）and elite parents popularised and applied in south China and the multi-site test of national soybean region.The resistance identification was classified into five grades.The result of the disease index suggested that Chengxian43,Huachun5,Huaxia17,Huaxia2,Huaxia9,Jiaoda14,Jiaoda18,Liaoxiandou18,Shoudou38,Zhe Nong8,Zhexian16,Zhonghuang24,Zhonghuang325 and Zhongpin661 were all less than 15%,which showed high resistance.Eventually,the parents Zhonghuang24 and Huaxia3 with very significant phenotypic differences were selected to construct Recombinant Inbred Lines（RILs）.High-density genetic maps which based on the RILs were constructed by using RAD resequencing technology.Soybean mosaic virus strain SC18 was inoculated into RIL population.The results of Chi-square analysis by Excel were consistent with the theoretical value of 1 resistance:1susceptibility.All F₁ strains derived from a cross of Zhonghuang24 and Huaxia3 were inoculated with soybean mosaic virus strain SC18.Among them,11 strains showed resistance to the disease and F₂ showed the isolation ratio of 3R:1S,which proved that the resistance to SC18 was controlled by a single dominant locus.The resistance of Recombinant Inbred Line population for mosaic virus SC18 was detected in the genome-wide range using composite interval mapping method（CIM）on the Win QTLCart software.The soybean mosaic virus SC18 resistance gene was mapped to a major locus on the bin 65 region of chromosome 13 with 79.5 c M of the genetic distance from the starting marker locus,37.43 of the LOD value,and 62.01%of phenotypic variation.There were 30 genes in the location interval searched on NCBI and Soybase databases.Three candidate genes with disease resistance structure type,including Glyma13g150000,Glyma13g151100 and Glyma13g21640,were identified on chromosome 13 of the main locus according to the gene functional annotation.However,the function of resistance to SC18 strains needs further verification.