Identification And Genome-wide Association Analysis Of Grain Shape And Grain Weight In Population Of Wheat Varieties

Wheat（Triticum aestivum L.,AABBDD）is an important ration crop in the world and in China.In the current situation where wheat demand is growing faster than production,it is critical to increase wheat yields.Thousand Grains Weight（TGW）is one of the three elements of wheat yield and is mainly controlled by grain shape factors such as seed size.Wheat grain shape traits include Grain Length（GL）,Grain Width（GW）,Grain Thickness（GT）,etc.In this study,a genome-wide association study（GWAS）was conducted to obtain marker loci associated with grain shape and grain weight traits and to predict their candidate genes based on the SNP markers developed by the group.（1）Identification of grain shape and grain weight in populations of wheat varieties.Seven grain shape and grain weight traits,including thousand grain weight,grain length,grain width,grain thickness,aspect ratio,length-thickness ratio and width-thickness ratio,were identified in272 wheat varieties（lines）.Analysis of phenotypic variance showed that each trait exhibited large variation with an average coefficient of variation of 4.82%,the largest variation in thousand grain weight（19.17%）and the smallest variation in grain length（2.35%）.The heritability of all seven traits was greater,with an average heritability of 54.10%,a maximum of 79.7%（grain length under water-saving treatment）and a minimum of 33.3%（grain width under water）.The correlation analysis showed that there was a highly significant/significant positive correlation between grain weight and grain length,grain width,grain thickness and width-thickness ratio,and the effects on thousand grain weight were,in descending order,grain width > grain thickness > grain length > width-thickness ratio.Among the 272 wheat materials,109,146,173 and 73 varieties with higher thousand grain weight,grain length,grain width and grain thickness traits than Jemima 22 were screened,respectively;154,92 and 40 varieties with lower aspect ratio,length-thickness ratio and width-thickness ratio traits than Jemima 22 were screened among the 272 wheat materials.（2）Genome-wide association analysis of grain shape and grain weight in wheat variety populations.The genome-wide association analysis detected a total of 460 markers that were stably and significantly associated with wheat grain shape and grain weight on all 21 chromosomes,explaining 4.69% to 21.39% of the phenotypic variation.Among them,32,154,13,26,125,94,and 16 markers were detected to be significantly associated with thousand grain weight,grain length,grain width,grain thickness,grain aspect ratio,grain length-thickness ratio,and grain width-thickness ratio,respectively.Sixteen markers,including S＿008446,were detected to be significantly associated with at least three traits simultaneously as pleiotropic markers.（3）Prediction of candidate genes for grain shape and grain weight.The obtained stable significant SNP markers were analyzed for Chinese spring genome annotation,and six candidate genes for grain shape and grain weight were identified: Traes CS1A02G407700（serine/threonine protein kinase）,Traes CS1A02G415300（mitogen-activated protein kinase）,Traes CS1A02G402400（mitogen-activated protein kinase）,Traes CS4B02G044600（phycocyanin structural domain-containing protein）,Traes CS7A02G416400（coenzyme response factor）and Traes CS5B02G53830（flavin monooxygenase-containing YUCCA11）.