Association Mapping Of Yield-related Traits In Barley (Hordeum Vulgare L.) And Analysis Of Allelic Effects

It is of great significance to explore the inherent genetic mechanisms of yield-related traits of barley and the correlations among each other,as which helps us to elaborate the process of yield formation and provide theory for breeding seletion.Previous researches were mainly focus on the effect of rbcS gene on plant photosynthetic rate,nevertheless,few studies were reported about the influence of this gene on the grain-related traits which are closely associated with photosynthesis.In this work,one hundred and twelve barley materials of current cultivars and advanced breeding lines were grown in three different environments and 8 yield-related traits including days to heading,plant height,grain number per spike,spike length,thousand grain weight,grain length,grain width and length to width ratio of grain were collected to asesse the genetic mechanisms of yield-related traits and the correlations among each other.Furthermore,the genotypes of 112 lines were assessed by SSR markers,and association mapping of 8 target traits with SSR loci was caculated based on population structure and LD analysis.At last,association maping of grain-related traits with HvrbcS gene was evaluated based on SNP variace and allel effects were analysised for SSR loci and SNP which were detected in more that two environments.The main results are as following:1?Heritability analysis showed that thousand grain weight and length to width ratio of grain had highest broad heritability(the value were more than 80%).Days to heading,grain number per spike,spike length and grain width had moderate broad heritability of which the values were vary from 60% to 80%.However,the broad heritability of plant height was lower than others.Analysis of variance revealed variation of all 8 traits invested in this study was originated from genotypic variation,whereas environment variances were significant for all traits.Moreover,genotype by environment interaction variance was also significant for plant height and grain length reflecting that different genotypes had different sensitivity to environmental alternatives.Correlation analysis results indicated that thousand grain weight of leptosomatic grain was lighter than oblate or elliptic ones,whereas comepared to shape,it seemed that thousand grain weight was greatly influenced by size.In addition,grain weight and grain shape were strongly affected by spike length.2?112 materials were divided into two subpopulation based on population structure analysis which showed that these two subpopulation were coincide with naked barley group and hulled barley group,respectively.LD analysis manifested that population structure will decrease LD significance(P values),neutralize LD value and magnify LD decay distance and it also revealed that 4H and 6H choromosomes of barley had very high LD which reflected part of genomic regions on these chromosomes were once subjected to strongly selection pressure.LD decay analysis reslut displayed LD decay distance of naked barley and hulled barley were 8.2 cM and 7.4 cM,respectively.3?Association analysis detected out 9,5,3,7,8,7,8 and 1 loci related to days to heading,plant height,grain number per spike,spike length,thousand grain weight,grain length,grain width and length to width ratio of grain QTL,respectively and the majority of significant loci were consistent with previous reports.Of those loci,GBM061 locus associated with a major QTL of days to heading which was near by the gene of vernalization(VRN-H1)explained phenotypic variation up to 25.3% and 25.0% based on Q+K and PC+K models,respectively.Moreover,GBM1468 locus lined to thousand grain weight QTL and Scssr10226 locus releated to grain width QTL which are insensitive to environments were dected out in this study.Allele effects analysis illuminated that GBM1468-A2 with representative accession FB0648 decreased thousand grain weight significantly in three enviroments,range from 6.8 g to 8.3 g,with an average of 7.5 g.At the locus of Scssr10226,accessions carrying A2 allele with representative accession FB0226 averaged 0.21 mm of grain width improvement,while A3 with representative accession FB0647 decreased the grain width with an average of 0.19 mm.4?Frequency of variance of HvrbcS gene in 3‘-UTR was higer than first extron,intron and second extron significantly.Association mapping detected out 5 SNPs which were insensitive to environments and detected by more than two models including SNP-757 related to grain length,SNP-757 related to grain width,SNP-824 related to thousand grain weigth,SNP-824 related to grain length and SNP-824 related to grain width.Interestingly,all of them were located in 3‘-UTR.SNP effects analysis showed that SNP-757-A improved longer grain length and wider grain width with an average of 0.33 mm and 0.11 mm,respectively.While the lines in SNP-824 locus carrying A base increased thousand grain weight,grain length and grain width with an average of 3.96 g,0.43 mm and 0.10 mm,respectively.