Association Mapping And Linkage Mapping Of Resistance To Soybean Mosaic Virus

Soybean?Glycine max?L.?Merr.?is an important food and oil crop,but soybean mosaic virus?SMV?disease is one of the most serious and broadly distributed soybean disease,leading to yield loss and seed quality deterioration significantly.so far,developping resistant soybean cultivars is the most effective,economical,and environment friendly approach for controlling this disease.Therefore,screening for resistance source to SMV,mapping the resistance genes/QTL and analysis of the candidate genes are are very important for breeding resistant varieties.In order to map the resistance genes for SMV,we screened a lot of resistance soybean source for SMV strains SC3 and SC7 for breeding resistant varieties.We identified a lot of loci associated with resistance to SMV via association mapping using SSR and SNP markers.Based on the primary mapping of RSC7 on the chromosome 2?Fu et al,2006?,we fine-mapped the resistance gene RSC7,and analyse the candidate genes via qRT-PCR for confirming the resistance gene RSC7.This research could supply useful information for map-based cloning of resistant genes and soybean breeding for disease resistance 1.Screening for resistance soybean source for SMV strains SC3 and SC7In this study,219 soybean accessions including breeding lines and landraces were inoculated with SMV strains SC3 and SC7,28?12.8%?soybean accessions were found resistant to SC3,and 14?6.4%?soybean accessions were found resistant to SC7,while 10?4.6%?soybean accessions were resistant to both SC3 and SC7.The soybean accessions resistant to SC3 and SC7 will be usful for breeding resistant varieties and mapping resistance gene.We also discovered that the breeding lines were more resistant to SMV than landraces.2.Association mapping for resistance to SC3 and SC7 using SSR markersAssociation mapping was conducted with 196 soybean accessions to indetify QTLs for resistance to SMV strains SC3 and SC7 using 205 SSR markers.The resluts showed that 40 SSR-resistance associations were detected using the Q+K model,involving 30 SSR markers,22 SSR markers of them associated with resistance to SC3,18 SSR markers associated with resistance to SC7,and 10 SSR markers associated with resistance to SMV strains SC3 and SC7.Two SSR markers associated with the resistance to two SMV strains were detected in all environments.Of the SSR markers associated with resistance to SC3,several SSR markers were located as a cluster on chromosomes 6 and 7;while several SSR markers associated with resistance to SC7 were also located as a cluster on chromosomes 6 and 7.Among the 10 SSR markers associated with the resistance to two SMV strains,several SSR markers were located in a adjacent region,such as satt365?satt319 and satt658 on chromosome 6,and CSSR306?sat₃16 and satt201 on chromosome 7.Both of these regions may contain the resistance gene to SMV.3.Association mapping for resistance to SC3 and SC7 using SNPsOne hundred and ninety one soybean accessions were used for detecting the SNPs associated with resistance to SMV via association mapping.The results indicated that 37 SNP-resistance associations were indetified by two models?PCA+K,Q+K?,involving 31 SNPs,14 SNPs of them associated with resistance to SC3,23 SNPs associated with resistance to SC7,and 6 SNPs associated with resistance to SMV strains SC3 and SC7.When we analyse the locations of these SNPs,we found that some SNPs associated with resistance to SC3 were located as a cluster on chromosomes 9?15?18 and 20;while several SNPs associated with resistance to SC7 were located as a cluster on chromosomes 3?8?18?19 and 20.Some of the SNPs associated with resistance to SMV strains SC3 and SC7 were also located in a adjacent region on the chromosome 18 and 20.Thus,there may be QTLs or genes associated with resistance to SMV in these regions.4.Fine-mapping of RSC7Based on the primary mapping of RSC7 on the chromosome 2?Fu et al,2006?,we fine-mapped the resistance gene RSC7 between SSR markers BARCSOYSSR₀2₀621 and BARCSOYSSR₀2₀63,and the physical distance btween them was less than 200 kb.Fifteen putative genes exist within this region depend on the Williams 82 soybean sequence annotation database,and only one gene contain the LRR domain.After analysis of the candidate genes via qRT-PCR,we found that the expression level of eleven candidate genes changed significantly in the post inoculated with SC7 between the two parents,which could provide usful information for map-based cloning of resistance gene in the future.