Genome-wide Association Analysis Of Sugar Contents In Brassica Napus L.

Rapeseed(Brassica napus L.)is an important oil crop in China,and double low rapeseed varieties have vegetable value.At present,rapeseed bolting has been popular in some areas.Compared with other bolting vegetables,the quality of rapeseed bolting is still insufficient.In this study,the sugar content of natural population(505 materials)of B.napus at two experimental sites(Ezhou and Wuhan)was investigated.Combined with genome-wide association analysis,multiple SNP loci significantly associated with sugar content were located,and the candidate genes were predicted.At the same time,the soluble sugar and other traits of 300 self-bred double-low rapeseed materials were investigated,and the genome-wide association analysis was performed using 50 K chip data.The main results are as follows:1.Phenotypic variation analysis of carbohydrate content in natural populations showed that the variation coefficient of each phenotype was large.The changes of carbohydrate content at seedling stage and bolting stage were consistent at the two test points.Compared with seedling stage,the content of starch increased and the content of soluble sugar and sucrose decreased at bolting stage.The starch content changed little between the two test points,indicating that the trait was less affected by the environment.The correlation analysis of carbohydrates showed that the correlation among starch,soluble sugar and sucrose content at seedling stage was significant,while the correlation among some traits at bolting stage was not significant.2.Genome-wide association analysis identified multiple SNP loci related to starch,soluble sugar and sucrose content.Among them,81 SNP loci were significantly correlated with starch content,73 SNP loci were significantly correlated with sucrose content,and 28 SNP loci were significantly correlated with soluble sugar.A total of 4645 genes were identified by further excavation of the genes within 100 kb upstream and downstream of the screened SNP loci,of which 502 genes were related to glucose metabolism,including genes related to glucose synthesis and metabolism,such as SWEET10,SUC2 and SUS6.3.In this study,the phenotypic variation of carbohydrates in 300 self-bred ’ double low ’ rape varieties was analyzed.The variation trend of carbohydrates from seedling stage to bolting stage was consistent with that of natural population,and the average sucrose content was significantly higher than that of natural population(47.4 mg/g v.s.30 mg/g)The variation coefficient of carbohydrate content ranged from 25.27% to 38.22%,which was significantly lower than that in natural populations.Genome-wide association analysis was not associated with significant SNP loci,which might be due to reduced genetic diversity due to artificial selection.In this study,phenotypic variation variation of carbohydrates in natural populations and ‘ double low ’ cultivars was analyzed,and multiple candidate genes affecting the accumulation of carbohydrates in rapeseed were screened combined with genome-wide association analysis,which laid the foundation for the genetic research of carbohydrates in rapeseed and the improvement of taste of rapeseed cultivars.