Genome-wide Association Analysis Of Flour Processing Quality Traits Related Of Triticum Dicoccoides And Cloning Of High Molecular Weight Glutenin Subunit Gene 1Ax1

As an important gene resource for wheat improvement,wild emmer(Triticum dicoccoides L.,2n=4x=28,AABB)is considered to be the donor of the common wheat(Triticum aestivum L.,2n=6x=42,AABBDD)AABB genome,which contains many valuable properties,including high protein content,strong disease resistance,strong tillering ability.Flour quality traits are quantitative traits controlled by multiple genes,which are significantly influenced by environment.Thus they display a continuous phenotypic variation.The beneficial loci of wild emmer are obtained through genome-wide association analysis for flour processing quality by high density SNP markers.These loci can provide benificial genes of wild emmer,it can also enrich new gene resouce for improving wheat flour processing quality.In this study,121 wild emmers which were harvested from the Middle East were applied to 3 test sites,encompassing Huixian,Shangqiu and Kaifeng.Genome-wide association analysis of wild emmers provided excellent sites of flour processing quality through A and B genome polymorphism of wheat 55K SNP chip.Moreover,the gene 1Ax1 of wild emmer J129 was cloned by a directional deletion subcloning technique.The main results are as follows:(1)By analyzing and investigating flour processing quality traits of 121 wild emmers which include grain starch content,grain protein content,wet gluten content,sedimentation value,water absorption,gluten index and flour extensibility traits,the above results indicated that 7 quality traits had wide variation.The maximum variation coefficient was the flour extensibility(FE),33.42%,and the minimum was grain starch content(GSC),5.84%.The results of variance analysis showed that 7 quality traits among the genotype differences,environment diffrence and their interaction reached a significant effect.Generalized heritability analysis showed that the grain protein content(GPC)genetic maximum rate was 32%;water absorption(WA)genetic minimum rate was 11%.The grain protein content was very significantly positive correlated with wet gluten content and sedimentation value.Wet gluten content and water absorption showed significant positive correlation.Simultaneously.There were significant positive correlation between flour extensibility and grain protein content.Gluten index was very significantly negative correlated with grain protein content and wet gluten content.(2)Based on the 10907 high-quality polymorphic SNP markers from the A and B genomes in the wheat 55K SNP chip,Genome-wide association analysis of 121 wild emmers showed that 1840 loci identified were significantly associated with flour processing quality traits,including 714 segments.These SNPs were distributed on the 1-7A and 1-7B chromosomes of wild emmer,and the overall interpretation rate of phenotypic variation(R~2)for all associated loci was 8.3%-26.4%.Sixteen stable segments/sites(three segments)associated with grain starch content were distributed on chromosomes 1A,4A,1B,3B,4B,and 5B.The number of 1B(372.30-374.91 Mb),4A(121.05-121.21 Mb),and 5B(142.67-144.87 Mb)chromosomes were in the lead.Fourteen stable segments/sites(one segments)associated with grain protein content were distributed on chromosomes 2A,3A,4A,5A,6A,3B,6B,and 7B.The number of 7B(50.30-50.78 Mb)chromosomes took the leading position.One stable segment associated with wet gluten content was distributed on chromosomes 7A(510.65-510.83 Mb).One stable site associated with sedimentation value was distributed on chromosomes 1B,and its physical location was 289.53 Mb.Five stable sites associated with flour extensibility were distributed on chromosomes 1A,2A,6A,3B,and 6B,and their physical locations were 518.77 Mb,95.16 Mb,74.45 Mb,23.38 Mb and 16.40 Mb.In addition,candidated gene prediction and functional annotation were performed on the SNP loci,which were associated with the relevant traits of 121 wild emmers.The results indicated that these loci are mainly related to disease proteins,cytochromes,transporters,structural proteins and protein kinases.(3)The gene 1Ax1 of wild emmer J129 was cloned by a directional deletion subcloning technique.By analysing and comparing sequences of HMW glutenin subunit Ax gene sequence,the result showed that J129-1Ax1 gene sequence with the published HMW-GS subunit gene have a consistent structure.The amino acid sequence of Ax compared with other subunits,it had one unique gene sequence of PTQGQQGQQ.The structure might affect the formation and stabilization of protein domains.In addition,the J129-1Ax1 subunit of glutamine(Q),α-helixes’andβ-strands’content were higher,suggesting that the gene might increase quality.