Gene Diversity And Development Of Molecular Markers Based On Resistant Candidated Gene Rhg1 To Soybean Cyst Ematode (Heterodera Glycines Ichinohe)

SCN (Soybean Cyst Nematode, Heterodera glycines Ichinohe) is a seriously destructive pest in soybean production in the worldwide. Planting resistant soybean cultivars has been proved as an economical and effective method to decrease or avoid its damage. Markers developed from resistant gene could identify SCN resistance effectivly and accelerate the breeding process. rhgl gene can explain more than 50% resistance of SCN3 as the candidate resistant gene to SCN. In this study, we first analyse rhgl and it's homologous sequence of 5 soybeans in order to clarify copies of rhgl on soybean genome and evolution model; Second we evaluate the gene diversity and peform association analysis between rhgl and the resistance-susceptibility of SCN by GLM method of 57 cultivar soybeans, aiming at clarifing occurring frequency of SNP and distributed characters as well as finding SNPs linked to SCN resistance; in the end we develop InDel markers linked to SCN resistance according to the InDel polymorphism sites in 57 soybeans, in order to properly utilize of soybean germplasm in soybean improvement. The main results are as follows:1. Illustrating the relationship between rhgl and it's homologous gene. We clone the rhgl gene and its homologous gene by use of perennial wild soybeans (2), annual wild soybean (1), resistant landrace (1) and susceptible bred cultivar (1), there are two homologous genes on Gmll and Gml8 chromosome. The gene domain prediction of rhgl-Gmll and rhgl turns out that they both have the resistant gene structure LRR-Transmembrane-STYKc. We presume that the model of novel gene arising may be the EAC-model, and the rhgl-Gmll is the ancestry gene maintaining the ancestry function.2. Illustrating the DNA diversity of rhgl and its distribution in cultivar soybeans. We clarify the sequence polymorphism of 57 rhgl, there are 59 substitutions and 4 InDels among the total 63 SNPs.3 Non-synonymous mutations occur in the STYKc domain of the total 9 Non-synonymous sites. The sequence diversity of landrace (π=0.00335,θ=0.00273) is much higher than that of bred cultivars (π=0.00206,θ=0.00227), which shows that rhgl in bred ciltivars is affected by artificial selection. Haplotype analysis show HAP-3 and HAP-4 are resistant and major haplotypes in 57 soybeans.3. Scanning SNPs linked to SCN resistance. Association analysis show there is genetic structure in 57 cultivar soybeans, fouthermore there is 1 SNP (2480G/A) associated with the resistance of SCN significantly at 0.05 level. However this SNP is synonymous in the kinase domain, the mechanism of its resistance needs more research.4. Development of InDel markers linked to SCN resistance. Among four InDel loci detected by comparing sequence analysis of rhgl three InDel loci were used to develop InDel markers. rhgl-I4 is associated with the resistance-susceptibility of SCN. Identification efficiency of SCN resistance combing rhgl-I4 with Satt309 is 88.2%, which increases the Identification efficiency of MAS significantly.