Identification And Utilization Of Novel Genes Resistant To Soybean Cyst Nematode

Soybean cyst nematode(SCN)is a parasitic nematode in soybean root,which causes serious damage to soybean in the worldwide.SCN3 is the most widely distributed among the 16 races that has been identified.A large number of studies and practices have shown that crop rotation and planting resistant varieties can control losses effectively.Soybean cyst nematode disease is a complex quantitative trait controlled by major genes and multiple minor genes.Studies have shown that the two major cloned genes,rhg1 and Rhg4,could only explain resistance mutations of about 60%,and aggregation of other disease-resistant alleles could increase resistance effectively.Moreover,the overuse of a few single resistant sources results in a single resistance of resistant varieties,of which,the SCN population could overcome resistance and form new populations through mutation and recombination.These easily lead to loss of resistance and outbreak of new physiological races,resulting in the worse Area and reduction in production.Therefore,it is necessary to strengthen the exploration and utilization of minor and multi-gene resistance sources,and comprehensively utilize major and minor genes to maintain the persistence and stability of SCN resistance in soybean production.In this study,based on the recombinant inbred lines and lineage materials of Zhongpin 03-5373,an excellent resistant source,linkage analysis and pedigree analysis was used to discover new SCN resistance genes and finely map/clone SCN3-1 and SCN3-11.Through the development of functional markers,we could analyze the distribution characteristics of disease-resistant alleles in domestic and foreign resistant and sensitive resources.Molecular marker-assisted selection and polymerization techniques were used to breed SCN resistant cultivars to provide genes,markers and parents to accelerate the development of novel SCN resistant varieties.The key research findings are as follows.(1)High-density Bin map was constructed by low-depth re-sequencing analysis of recombinant inbred lines derived from the excellent resistance variety Zhongpin05-3373 and susceptible variety Zhonghuang13.The total distance was 2,807.59 c M and the average genetic distance was 0.63 c M.Combined with SCN3 resistance accuracy identification results,we mapped to three QTLs(SCN3-1,SCN3-11 and SCN3-18),located at chromosome 1,11 and 18,respectively,and their phenotypic variation between 4.7% and 17.9%.Among them,SCN3-1 is a novel disease resistance site,which could explain 5.8% of the phenotypic variation and the interval is 4 Mb.(2)A total of 373,346 InDel was identified by 15 X re-sequencing using Zhongpin03-5373 and its 10 parents.Using the phylogenetic tracing,a total of 1931 SCN3 resistance-related sites,including the new resistance site SCN3-1,were identified to verify that SCN3-1 was associated with SCN3 resistance,and resistant allelic came from PI 437654.We developed 5 CAPs and 4 In Dels markers within the SCN3-1 interval and identified the Zhongpin03-5373 recombinant inbred line to fine-mapping SCN3-1 to 9.5 kb,including two candidate genes,SCN3-1-A and SCN3-1-B.(3)A alternative splicing site was detected by comparing the CDS sequence of the functional gene of SCN3-11,Gm SNAP11,a co-dominant CAPs marker,Gm SNAP11-2565,was developed based on this variable site sequence.Combining with the molecular markers of Gm SNAP18(rhg1)?Gm SHMT(Rhg4)and SCN3-1,we analyzed 176 soybean germplasms with a known disease-resistant phenotype.Molecular marker selection based on three markers(Gm SNAP11?Gm SNAP18 and Gm SHMT)could effectively maintain high levels of disease resistance.