Genome-wide Association Analysis Of Wheat Gliadin Content

Wheat is an important staple crop,which plays an important role in ensuring the absolute food security of China.With the rapid development of national economy,the market demand for high-quality wheat is increasing.The processing quality of wheat mainly depends on gluten,and gliadin is one of its two major components,accounting for about 60% of gluten content.Gliadins are composed of α-,γ-and ω-gliadin and each of the compositions is encoded by multiple loci.The content and composition of gliadins have an important influence on the viscosity and ductility of dough.Therefore,it is of great theoretical significance and application value to analyze the genetic basis of gliadins content and explore excellent genetic loci for high quality wheat breeding.In the present study,a natural population consisted with 207 wheat varieties collected world-wide was planted under two locations for two years.The content of gliadins and its compositions were determined by RP-HPLC.Combined with wheat 660 k SNP chip,the genome-wide association study(GWAS)was carried out by using mixed linear model.The main results are as follows:1.The content of total gliadins and its three compositions in the four environments varied widely,ranging from 17.92 to 59.20%;the largest variation coefficient derived from the content of ω-gliadin,which was 59.20% while the smallest variation coefficient was from the content of total gliadin,which was 17.92%.The broad heritability of the gliadins and its three composition content was 74.32-87.38%,which indicated that it was mainly controlled by genetic factors.The contents of all the four traits distributed continuously,demonstrated normal or partial normal distribution which indicating all those traits were controlled by multiple loci.2.Totally,158 SNPs were detected significantly related with the content of total gliadin and its three compositions by GWAS.For the content of total gliadins,14 significant SNPs were detected and the locus Qgli2 B.2 on chromosome 2 which accounting for 17.25% had the largest contribution to phenotypic variation.In addition,65 SNPs were detected significantly associated with the content of ω-gliadin,and the largest contributing loci,Qωg1D.2,on chromosome 1D accounted for34.85% to the phenotypic variation.16 SNPs were screened significantly associated with the content of α-gliadin,among them the Qαg6A.2 was the largest contribution loci which accounting 18.06% for the phenotypic variation.For the γ-gliadin content,63 significant SNP locis were detected and the largest contribution locus was Qγg1D.1 conferring 28.96% to the phenotypic variation.3.A total of 13 pleiotropic locis which contributing to more than 2 traits were detected,distributed on 9 chromosomes,including 1A,1B,1D,2B,3B,4B,5B,6D,and 7A.Among them,the loci located on chromosomes 1A and 4B,co-localized the genetic loci of total gliadin content,ω-gliadin content,and γ-gliadin content.The candidate gene Traes CS1A02G007300 annotated the function of γ-gliadin coding was identified in the segment located at the associated site on chromosome 1A,and it was found that its expression level was significantly positively correlated with total gliadin content and γ-gliadin content.Based on the sequence associated with SNP(AX-110377433),a KASP marker was developed and the alleles’ divergence of the SNP clearly discriminated the expression of Traes CS1A02G007300,total gliadin content,and gamma-gliadin content in wheat materials,significantly.In another two natural populations,it was also found that there was significant differences in the total gliadin content and γ-gliadin content between the different alleles of AX-110377433.4.Using Traes CS1A02G007300 expression level to perform genome-wide association analysis,a total of 54 SNPs significantly related to their expression levels were detected.Those SNPs were mainly distributed on all chromosomes except 4B,4D,and 5D,of which the SNP(AX-94812509)on chromosome 1A was the largest contribution locus with the phenotypic variation of 15.32-47.17%.Combined with GWAS of the gliadin content,32 SNPs simultaneously controlled the gliadin content and the expression of Traes CS1A02G007300,indicating that Traes CS1A02G007300 is the key factor affecting the gliadin content.