Identify Soybean Mosaic Virus-Recombination Isolate And Mapping And Functional Analysis Of SMV Resistance Gene

Soybean mosaic virus （SMV） is one of the most broadly distributed diseases worldwide. It causes severe yield loss and seed quality deficiency in soybean and this viral disease prevalent in soybean cultivar regions. SMV is consist of a single positive RNA strand with high variation, recombination events is likely to be occur and form a new type of virus when SMV infect soybean with other virus. It is important that understand and clear the information on new types of virus and monitor the dynamic changes of the virus for preventing virus prevalence. Utilization of resistant varieties is the most economical and environmentally safe method for controlling this disease. The success and failure of breeding resistant varieties depend on resistant resources, molecular mapping of resistance genes and the realization of inheritance mechanisms of resistance to SMV strains.Therefore, the purpose of this study is to monitor the dynamic changes of SMV strains in Chinese soybean cultivar regions, systematic identify and evaluate the hazard of the new type virus, provide the necessary information for preventing and controlling the prevalence of virus; study on the inheritance of resistance to SMV and molecular mapping the resistance gene, study the mechanism of disease resistance genes, solve the debate of "one gene control one strain SMV resistance" or "on gene can control multi strains SMV resistance"; Meanwhile, the mRNA expression profiles of the candidate genes were analyzed by quantitative real-time polymerase chain reaction （qRT-PCR）, determine the soybean functional resistance gene mapped cloning and improve the resistance of soybean through transgenic technique.The main results were as follows:1. Discover and identify the new type SMV isolate150SMV isolates or virus samples from different provinces were analyzed and a new type of SMV isolate,4469-4, was discovered. Whole genome of4469-4was sequenced, it consist of9994nucleotide （nt） and only one open reading frame,4469-4has405or406nt more than SMV genome has been reported and translation to form a poly protein of3202amino acids（aa）, the protein cleave sites was consistent with reported SMV isolates. In5’UTR region of4469-4, it has a highest homologous with BCMV, P1region of4469-4has highest homologous with WMV at both nt and aa level. Besides5’UTR and P1region,4469-4with highest homology to SMV isolates at nt and aa level.Recombination point was analyzed on region of5’U+P1+HC-Pro indicated that:a recombination point was detected at770nt position. Before770nt,4469-4has a highest homologous with BCMV and the other has a highest homologous with SMV, this indicate that4469-4was origined from recombination between BCMV and SMV. Phylogenetic of nucleotide （nt） sequence comparison among related isolates in whole genome regions indicate it has closely phylogenetic relationship to SMV and it belong to SMV, but consider the characteristics of recombination, we suggest designated4469-4as a SMV-R type isolates of SMV.The pathogenicity ability and host range of4469-4and Sc6indcated that:44469-4induces mild mosaic on most soybean cultivars and system necrosis was observed on a few cultivars; Sc6can induce multi symptoms such as mild mosaic, serious mosaic and system necrosis.4469-4can infect most of the tested soybean cultivars; Sc6can also induce mosaic on common bean, red bean, mung bean, horsebean and pease, but4469-4can only infect common bean and pease. It is suggest that the two isolates have different on its host range and pathogenicity ability.The type of the150SMV isolates or virus samples from different provinces were analyzed, the results indicate that:27isolates or virus samples were or contain SMV-R type virus. In these isolates, only one from Hebei province, the others from the southeast coast or southwest of China. Most of the SMV-R type virus from Sichuan, Jiangsu, Zhejiang provinces and Chongqing, these indicates that SMV-R type virus may origins from the south of The Yangtze River.2. Genetic analysis and mapping of four resistance genes in PI96983Segregation analysis indicated that single dominant genes （designated as RSC3, RSC6, RSC7and RSC17） controlled the resistance to SC3, SC6, SC7and SC17, respectively. Genetic maps revealed that RSC3, RSC6and RSC17are located between the SSR markers BARCSOYSSR₁3₁114and BARCSOYSSR₁3₁136with distance0.799cM,1.209cM;1.102cM,0.580cM and1.247cM,1.096cM respectively; whereas RSC7is located between the SSR markers BARCSOYSSR₁3₁140and BARCSOYSSR₁3₁185with distance0.035cM and2.026cM. Further recombination lines （RLs） map RSC3, RSC6and RSC17between SSR marker BARCSOYSSR₁3₁128and BARCSOYSSR₁3₁136with physical distance345kb; map RSC7between SSR marker BARCSOYSSR₁3₁140and BARCSOYSSR₁3₁155with physical distance381kb;The results also indicated that RSC7is not on the same locus as RSC3, RSC6or RSC17. Therefore speculated that the PI96983has two resistance mechanisms:"one gene control one strain SMV resistance" named Rsc-ps and "on gene can control multi strains SMV resistance" named Rsc-pm.3. qRT-PCR analysis of the resistance candidate genes in PI9698313SMV resistance candidate genes in PI96983were selected for qRT-PCR analysis base on results of mapping. After qRT-PCR analysis of the13resistance candidate genes, results suggest that1gene, Glymal3g26000, was presents related to SMV resistance.