QTL Mapping And Molecular Markers Development For Panicle And Stem Strength Traits For Wheat(Triticum Aestivum L.)

High yield is always the most important target in wheat breeding and production.Panicle traits of wheat,such as the grain number per spike and 1000-grain weight,closely correlated with the grain yield.Stem Strength is one of the major factors affecting production and lodging in wheat.Improving the quality of stem strength is an important way to increase kernel’s quality and yield potential in wheat.In the present study,the high-density genetic map constructed by 90 K SNP arrays,DArT technology,traditional molecular markers and the composite map（24,355 SNPs）based on the Illumina Infinium assay were used by combining linkage analysis and a GWAS for panicle traits.This approach was expected to enhance the validity and credibility of the QTLs of panicle and stem strength traits in wheat more than using linkage analysis or a GWAS alone.The main results of the present study as follows:（1）Thirty-five additive quantitative trait loci（QTL）were revealed,including eleven repeatable QTLs（QD1A.5-22,QFSN2 D.1-40,QL4 B.3-8,QFSN4 B.4-17,QGN4 B.4-17,QSL4 B.4-17,QTSS4 B.4-17,QGW4 B.4-17,QGW5 B.5-488,QL6 B.7-3 and QD6 D.2-1）on chromosomes 1A,2D,4B,5B,6B and 6D.The marker interval between EX_C101685 and RAC875_C27536 on chromosome 4B exhibited pleiotropic effects for GW,SL,GNS,FSN,SSN and TSS,with the phenotypic variation explained（PVE）ranging from 5.40% to 37.70%.（2）A total of 69 significant marker-trait associations（MTAs）were detected for panicle traits,which were distributed across all wheat chromosomes except for 4D,5D and 6D.six MTAs were consistently detected in multiple environments and were therefore regarded as relatively stable loci controlling these traits.Four multi-trait MTAs—RAC875_c9691₈70,wsnp_Ra_c19079₂8210937,BS00097939₅1 and RAC875_c56516₇86—were detected on 2A and 3A.（3）56 additive quantitative trait loci（QTL）were revealed,including 5 repeatable QTLs（Q2NJ1A.1-5、Q2CH2B.1-44、Q2ZJ4B.4-17、QWQD4B.4-13 and Q2CH6 B.1-13）on chromosomes 1A、2B、4B and 6B.The marker interval between EX_C101685 and RAC875_C27536 on chromosome 4B exhibited pleiotropic effects for S18 SBSL,PH,S27SBSLandT18 SBSL.（4）A total of 221 significant marker-trait associations（MTAs）were detected for panicle traits,which were distributed across all wheat chromosomes except for 4D and 6D.1 MTAs were consistently detected in multiple environments and were therefore regarded as relatively stable loci controlling these traits.Meanwhile,19 MTAs were detected in this study.（5）Consensus regions between RAC875_C27536₆11 and Tdurum_contig4974₃55 on chromosome 4B for GW in multiple environments,between QTSS5 A.7-43 and BS00021805₅1 on 5A for SD and TSS,and between QD3 A.2-164 and RAC875_c17479₃59 on 3A for SL and GNS in multiple environments were detected through linkage analysis and a genome-wide association study（GWAS）.In addition,six important QTL clusters on chromosomes 2D,3A,4B,5A and 6A were identified with high PVE% and good stability on a composite map.（6）According to the SNP marker,IACX557 markers were developed with restriction enzymes of AluI.Maker QWQD4 B.4-13 is validation results indicated that chain of molecular markers forstem strength,and which can be used for marker-assisted selection.