Genetic Structure And Diversity For Chinese Soybean (Glycine Max L.) Landraces In China And SNAPs Marker Development At Rhg1 Locus Underlying Resistance To Soybean Cyst Nematode

A better knowledge of genetic diversity and structure in soybean will be crucial for the utilization, conservation and management. In this study, a sample of 1863 soybean landraces which were widely distributed in China was analyzed at 59 SSRs loci. The genetic relationships among landraces were clarified in the molecular level. The core of germplasms was the diverse and abundant gene in the germplasms. For further utilizing germplasms, functional gene diversity were studied. Based on rhg1 locus which was detected as a major gene for SCN, a method for identifying and genotyping SNPs was constructed. The results were described as followed:1 The genetic clusters within soybean landraces were detected in the molecular level. A model-based clustering analysis assigned the landraces into seven distinct clusters and a mixed cluster. Among them, two clusters (SSpSM and SSuSM) whose accessions were mainly collected from mountainous southwest China were new distinct groups which could not be detected by variety classification methods. The genetic differentiation analysis showed that genetic separation had been shaped.2 Based on allele size comparison and phylogenetic analysis, we proposed that cultivated soybean was first domesticated in the middle-down stream of Yellow River, and subsequently spread southwardly and northwardly.3 All-length genome-sequence of rhg1 gene (5027bp) were obtained among six diverse genotypes. Total 21 SNPs were detected in coding and non-coding regions with a occurred frequency of 1 per 214 bp, corresponding to a nucleotide diversity (9) of 0.004673, and 1 per 164bp (θ=0.006098), respectively.4 Four groups of SNAP markers were developed based on mismatch base rule and used to analysis landraces, cultivars and foreign germplasms. The association analysis between resistance and SNAP markers showed that C mutation in rhg1-680 locus,C mutation in rhg1-748 locus and A mutation in rhg1-3983 locus were significant correlative with resistance in 0.05 level. However they also were detected on seven susceptible germplasms. Thus, it is necessary to develop haplotypes for SCN resistance.