Dissection Of Wheat Flavonoid Metabolic Pathway By Combining Linkage Mapping And Genome-wide Association Study

Flavonoids are a kind of important active substances in plants.They participate in the process of plants responding to biological or abiotic stress,and have the effects of anti-cancer,anti-oxidation and anti-ultraviolet.Wheat(Triticum aestivum L.)is one of the most crucial crops all over the world.It provides about one third of the calories and protein consumed by humans.However,wheat has not been fully studied in the analysis of flavonoids genetic structure.Metabolome quantitative trait locus analysis(mQTL)or metabolome genome-wide association study(mGWAS)can effectively analyze the internal genetic mechanism of complex traits,and has been applied in some crops.In this study,the metabolic profiles of mature grains in two wheat populations were analyzed by widely targeted LC-MS/MS.One of the populations was a wheat QTL mapping population(Yangmai 16 × Zhongmai 895)consisting of173 double haploid lines(linkage population).The other was a GWAS population consisting of 159 wheat accessions from worldwide(association population).Among the all metabolites detected,the flavonoids were the most.Collectively,78 flavonoids were detected and quantified.The content of flavonoids was regarded as phenotype for genetic analysis.The aim of this study was to find candidate genes that affect the content of flavonoids and control the flavonoids metabolic pathway in wheat by combining genome-wide association analysis with linkage analysis.Then verified the function of candidate genes through enzymatic activity and transgenic experiments.Based on analyzing the genetic structure of flavonoids,it also provides valuable information for molecular breeding of high-quality wheat.The main results are as follows:1.In linkage population,the broad-sense heritability of flavonoids ranged from0.07 to 0.84,and the coefficient of variation ranged from 16.97% to 154.16%.High density genetic map was constructed by wheat 660 K SNP for QTL mapping of flavonoid content in mature wheat grains.A total of 293 QTL related to the content of flavonoids were detected in 70 flavonoids,with the LOD value ranged from 2.51 to60.17.Single QTL could explain 1.35%-31.27% of the phenotypic variation.2.In association population,the broad-sense heritability of flavonoids ranged from 0.11 to 0.95,and the coefficient of variation ranged from 21.63% to 210.53%.Genome wide association studies were analyzed based on the wheat 660 K SNP with65008 effective SNPs.In total 480 significantly associated sites were detected for 69 flavonoids,with an average of 6.96 sites per metabolite.3.According to the co-localization results of mQTL and mGWAS of mr002(catechin),the MYB transcription factor Traes CS3D01G468400 was identified as a candidate gene,and the natural variation of the gene in the linkage population and its relationship with wheat grain color were clarified.4.According to the mQTL mapping results,the in vitro enzyme activity of the candidate gene glycosyltransferase Traes CS2B01G483900 was verified.According to the mGWAS mapping results,the key genes in flavonoids biosynthesis were identified such as chalcone synthase Traes CS2A01G035300,methyltransferase Traes CS3A01G534900 and their interaction with MYB transcription factor Traes CS1B01G279400 by EMSA.5.Combined with the mQTL and mGWAS mapping results of mr1072(luteolin6-C-glucoside),the in vitro enzyme activities of methyltransferase Traes CS2A01G051600 and glycosyltransferase Traes CS3B01G313400 and the continuous modification reactions of flavonoid methylation and glycosylation were analyzed.It is found that the methyltransferase Traes CS2A01G051600 has different activity from the methyltransferase reported in wheat,and can produce C7 methylation products,such as sakuranetin,which has disease resistance.In conclusion,based on mQTL and mGWAS we dissected the flavonoid synthesis pathway in wheat,which created favorable conditions for the next physiological function verification and genetic mechanism research,and laid a foundation for the biosynthesis and wide application of flavonoids,and provided a theoretical basis for cultivating wheat varieties rich in flavonoids.