| As the world’s largest ration crop,wheat（Triticum aestivum L.）is an important food source for human beings and an important source of protein.As the importance of wheat quality is also increasing,selection of quality wheat varieties and mining of quality genes have also become important breeding objectives for wheat genetic improvement.In this study,272 wheat varieties（lines）mainly bred in the Yellow and Huaihua wheat regions were used as test materials in recent years,and the quality traits related to protein and starch were measured,combined with the classification rules of wheat quality indexes in GB/T17320-2013 to screen out high-quality wheat varieties（lines）of strong gluten,medium-strength gluten,medium gluten.We also conducted genome-wide association analysis and weighted gene co-expression analysis to identify markers/candidate genes associated with wheat quality traits,which provided a basis for wheat quality breeding improvement and candidate gene cloning and functional studies.The main results are as follows:（1）Determination of wheat quality traits and screening of high quality wheat varieties（lines）.Fifteen quality traits such as protein content,dough rheology characteristics,sedimentation value,landing value and starch pasting characteristics were measured in 272 wheat varieties（lines）,and the analysis of the results showed that the variability of each trait was large（1.82%～80.01%）,with the largest coefficient of variation in stability time（ST）and the smallest coefficient of variation in pasting temperature（Pti）.Most of the correlations between proteinrelated traits showed a significant positive correlation,and most of the correlations between the related traits of starch gelatinization characteristics showed a significant positive correlation.Classification of wheat quality according to national standard GB/T17320-2013,7 strong gluten wheats,24 medium-strength gluten wheats（lines）and 91 medium gluten wheats（lines）were screened out.（2）Association analysis of quality traits.A genome-wide association analysis of quality traits was performed using TASSEL 5.0 software with a mixed linear model（MLM）with principal component analysis（PCA）and kinship as covariates,combined with genotype data of 176,357SNP/In Del markers that had been obtained by the group previously.The results showed that3392 loci,or 882 markers,were significantly associated with 15 traits at the p<0.00001 level on 20 chromosomes of wheat（except chromosome 4D）.the markers that are significantly associated with water absorption,developing time,stability time,sedimentation value,wet gluten content,grain gluten content,gluten index,peak viscosity,trough viscosity,break down,final viscosity,set back,peak time,pasting temperature,and falling number are respectively 5,368,625,165,9,5,451,10,15,22,17,13,26,18 and 14.118 markers were significantly associated with three traits and 136 markers were significantly associated with four traits,2markers were significantly associated with three traits and they were pleiotropy markers.（3）Weighted gene co-expression analysis.The transcriptome data of 272 wheat samples were normalized by FPKM,filtered out low confidence genes and filtered according to the mean standard deviation,resulting in 9473 genes for the construction of WGCNA.A total of 17 modules were screened out,and the correlation between modules and 15 quality traits was calculated.The darkred module and the lightgreen module were correlated for quality.GO and KEGG analyses of both modules revealed that both modules are involved in Carbohydrte metabolism,Lipid metabolism biological processes,which are related to wheat quality formation.And finally,twentyhub genes were eventually obtained for rice homologs that function in anther development,low-temperature resistance,ethylene molecular response,and inhibition of α-amylase. |
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