SNP And SSR Analysis And Genome-wide Association Mapping Of Drought Tolerance Trait In Brassica Napus

Rapeseed is a very important oil crop in our country, accurately and effectively identifying the genetic variation is very signality for elite germplasm discovery and molecular breeding. The popurse of this study is using SNP and SSR markers to genotype B. napus, construct a genotype database, analyze the genetic diversity of B. napus. Meanwhile, we got phenotype data through drought tolerance assessment, carried out genome-wide association study (GWAS) by phenotype and genotype data, and then obtained drought tolerance germplasm and markers which were related to drought tolerance.The main research contents and results are as follows:1. Genetic diversity analysis basing on SNP and SSR analysis in rapeseed.We used60k SNP array analysis platform and SSR capillary electrophoresis platform to genotype rapeseed resources.At last, we got26841high-quality SNP markers and70SSR loci after selection. We chose3900SNP from26841high-quality SNP markers and used the above70SSR loci to conduct population structure analysis and principal components analysis, the results of the SNPs and SSRs revealed that this population could divide into three parts, which were consistent with the three ecotypes classification, spring, winer, semi-winter ecotype,respectively.2. The genetic diversity analysis between A and C subgenome in natural and resynthesized B. napus. In this study,45high-quality SSR markers were screened and used to estimate the genetic base of a world-wide collection of248rapeseed inbred lines. For the whole collection, the genetic diversity of A genome was higher than that of C genome. The genetic diversity of C genome for the semi-winter type was the lowest among the different germplasm types. We evaluated the genetic diversity of25wild B.oleracea lines. More allelic variations and a higher genetic diversity were observed in B.oleracea than in rapeseed. One B. oleracea line and one oilseed B. rapa line were used to generate a resynthesized Brassica napus line, which was then crossed with six semi-winter rapeseed cultivars to produce7F1hybrids. Not only the allele introgression but also mutations were observed in the hybrids, resulting in significant improvement of the genetic base.3. Establishment the fingerprint identification standards in B. napus.We found that the more markers we used,the less accessions with high similarity coefficient were detected through statistical analysis.When the SSR markers up to35loci or SNP marker up to1900loci,the mumber of similarity accessions trends to be stable.4. GWAS on drought tolerance and root morphology diversity study on rapeseed. We assessed the drought tolerance of285inbredlines,2SNPs were detected on A7linkage group based on GWAS analysis. Because root characters were related to drought tolerance in previous study, root traits of307accessions were investigated. The results showed that the root morphology of this population can be classified into8representative types. Among these types (A-H), seed yield of type C and type D were higher than that of others.The research system of this study can be used for genetic diversity analysis and GWAS of drought tolerance in B. napus. It is meanful for revealing the rule of genetic diversity variation and discovering excellent germplasm or new genes.