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Fatty acids and oil contents in seeds are very important traits in rapeseed(Brassica napus L.)which is a typical representative of polyploid and an important oil crop.Understanding the genetic architecture of fatty acids and oil contents provides basis for improving quality in the process of rapeseed breeding.A panel of 189 inbred lines was grown in three years in Wuhan.The content of fatty acids and total oil in seeds were analyzed.Correlations were observed among compositions of fatty acids,especially between oleic acid(C18:1)and eicosenoic acid(C20:1)and erucic acid(C22:1).No significant correlations were observed between compositional fatty acid and oil content.Genome wide association studies on fatty acids and oil content were conducted in the panel of 189 inbred lines using 19,423 high-quality SNPs.Thirty loci were identified to be significantly associated with one or more fatty acids and/or oil content.Genes with known function in fatty acid biosynthesis or metabolism pathways were identified near these loci.Two loci corresponding to two orthologs of FAE1(fatty acid elongase 1)showed the strongest associations with all compositional fatty acids.Resequencing of the two known FAE1 genes controlling erucic acid identified causal SNPs and deletions in these two genes.Additionally,we further characterized candidate genes in another two previously unknown loci significantly associated with erucic acid.Causal SNPs and insertions/deletions were also identified through resequencing the two candidate genes.Our results revealed the genetic basis of oil biosynthesis in seeds of the tetraploid B.napus and may facilitate marker-based improvement for oil quantity and quality.