Single Nucleotide Polymorphism (SNP) Discovery and Association Study of Flowering Times, Crude Fat and Fatty Acid Composition in Rapeseed (Brassica napus L.) Mutant Lines Using Genotyping-by-Sequencing (GBS)

Rapeseed is the most important oil crop used in the food and biodiesel industries. In this study, based on single nucleotide polymorphism (SNP) identified from genotyping-by-sequencing (GBS), and an association study of flowering time, crude fat and fatty acid contents were investigated in 46 rapeseed mutant lines derived from gamma rays. A total of 623,026,394 clean data reads were generated with 6.6 million reads on average. A set of 37,721 filtered SNPs was used to perform gene ontology and phylogenetic analysis. Hierarchical cluster analysis of the rapeseed mutant lines gave eight groups based on flowering time and fatty acid compositions. Gene ontological analysis of the mutant lines showed that many genes displaying SNPs are involved in cellular processes, cellular anatomy, and binding. A total of 40 SNPs were significantly associated with flowering time (1 SNP), crude fat content (2 SNPs), and fatty acid content (37 SNPs). A total of 21 genes were annotated from fatty acid content SNPs; among them, nine genes were significantly enriched in reproductive processes, such as embryonic development, fruit development, and seed development. This study demonstrated that SNPs are efficient tools for mutant screening and it provides a basis that the improving the oil qualities of rapeseed.