QTL Mapping For Yield-related Traits In Wheat Based On Two RIL Populations

As one of the most important food crops in the world,wheat(Triticum aestivum L.)is an important source of protein,minerals and vitamins,providing food for more than 35% of the world’s population.However,due to the reduction of arable land,climate change and the rapid increase in population,wheat production cannot meet human needs.Therefore,increasing the yield potential has always been the main task of wheat breeding.This study is based on 50 K and 90 K gene chips,using F11:12 RIL populations "Xinong 1376 / Xiaoyan 81" and "Zhoumai 8425 B / Xiaoyan 81" containing 198 and 102 lines respectively as materials.Two RIL populations was planted in Yangling of Shaanxi Province and Nanyang of Henan Province from 2018 to 2020.Two high-density genetic maps were constructed using SNP gene chips covering 21 chromosomes of wheat.Complete Interval Mapping(ICIM)was used to analyze wheat yield-related traits in six environments.QTL mapping analysis is expected to lay the foundation for wheat molecular marker-assisted selection breeding,fine gene mapping and gene cloning.1.Two high-density genetic maps covering 21 chromosomes of wheat were constructed.A total of 2868 SNP markers were screened on the 50 K chip to construct a genetic linkage map,22 linkage groups were divided,the total length of the linkage group was 3945.34 c M,and the average genetic distance was 1.38 c M;a total of 1738 SNP markers were screened on the 90 K chip Used to construct a genetic linkage map,a total of 26 linkage groups are divided,the total length of the linkage group is 2068.80 c M,and the average genetic distance is 1.19 c M;2.In the detection of spike-related traits,176 QTL locis were located in the six environments of the two populations,which were distributed across the entire chromosome of wheat.Among them,98 QTL locis were located in Xinong 1376 / Xiaoyan 81 population and 78 QTL locis were located in Zhoumai 8425 b / Xiaoyan 81 population.A total of 36 locis controlling spike length,22 locis controlling total spikelet number per spike,27 locis controlling spike density,13 locis controlling fertile spikelet number per spike,18 locis controlling sterile spikelet number per spike,25 locis controlling grain number per spike,14 locis controlling spikelet fertility and 21 locis controlling grain number per fertile spikelet were detected in the two populations.A single locu could explain 1.29% ~ 50.74% of the phenotypic variation,including 66 major effect locis with phenotypic variation explanation rate greater than 10%,and 37 environmental insensitive QTLs stably detected in three or more environments.3.In the detection of grain-related traits,100 QTL locis were located in the six environments of the two populations.Except for 2D and 7D,they were distributed in the entire chromosome of wheat.Among them,56 QTLs were located in Xinong 1376 / Xiaoyan 81 population and 44 QTLs were located in Zhoumai 8425 b / Xiaoyan 81 population.A total of 33 sites for controlling thousand grain weight,35 sites for controlling grain length and 32 sites for controlling grain width were detected in the two populations.A single locu could explain 1.20% ~ 29.27% of the phenotypic variation,including 37 major effect locis with phenotypic variation rate more than 10%,and 9 environmental insensitive QTLs stably detected in three or more environments.4.In the detection of flag leaf-related traits,a total of 77 QTLs were located in the two populations under six environments.Except for 5B and 6D,they were distributed in the whole genome of wheat.Among them,54 QTLs were located in Xinong 1376 / Xiaoyan 81 population and 23 QTLs were located in Zhoumai 8425 b / Xiaoyan 81 population.A total of 31 sites controlling flag leaf length,22 sites controlling flag leaf width and 24 sites controlling flag leaf area were detected in the two populations.A single locu could explain 2.69% ~ 41.51% of the phenotypic variation,including 28 major locis with phenotypic variation explanation rate greater than 10%,and 11 environmental insensitive QTLs stably detected in three or more environments.5.A total of 208 QTLs were mapped in Xinong 1376 / Xiaoyan 81 population and 145 QTLs were mapped in Zhoumai 8425 b / Xiaoyan 81 population.Among the spike-related traits,the same QTL that controls spike length was detected in the two populations on chromosome 3A,and the QTL that controls grain number per spike detected on chromosomes 5A and 5B have a common interval.The QTLs that control the number of total spikelet number per spike,spike density,fertile spikelet number per spike,sterile spikelet number per spike,and grain number per fertile spikelet detected on chromosome 7A also have a common interval;Among the grain-related traits,the QTL that controls the thousand grain weight detected on chromosome 4A and the QTL that controls the grain length detected on chromosome 6B have a common interval;Among flag leaf-related traits,the QTL that controls flag leaf length detected on chromosome 3A and the QTL that controls flag leaf area detected on chromosomes 3B and 6B have a common interval.6.There were 35 major effect stable loci with phenotypic contribution rate greater than 10% which could be detected in multiple environments,including 1 site QSL-XX.2D that controls spike length,and 5 sites that control total spikelet number per spike QTSS-XX.5D,QTSS-ZX.2B,QTSS-ZX.6A.1,QTSS-ZX.6A.2 and QTSS-ZX.7A.2,4 sites for controlling spike density QSD-XX.2D,QSD-XX.5D,QSD-ZX.6D and QSD-ZX.7A.3,2 sites that control fertile spikelet number per spike of QFSS-XX.5D,and QFSS-ZX.2B,3 sites control sterile spikelet number per spike positions QSSS-XX.5A,QSSS-ZX.5A and QSSS-ZX.7A.1,1 site controlling the grain number per spike QGNS-ZX.2B,4 sites controlling spikelet fertility QSF-XX.5A.2,QSF-ZX.5A,QSF-ZX.7A.1 and QSF-ZX.7A.2,2 sites that control grain number per fertile spikelet QGNFS-ZX.5A,and QGNFS-ZX.7A.1,1 site QTGW-XX.4D that controls the thousand grain weight,3 sites QGL-XX.3A.1,QGL-XX.5D.2 and QGL-ZX.7B that control the grain length,2 sites controlling the grain width QGW-XX.4D and QGW-ZX.6A,2 sites controlling the flag leaf length QFLL-XX.1A.2,and QFLL-XX.5D.3,2 sites controlling the flag leaf width QFLW-XX.6B,and QFLW-ZX.3B,three sites that control the flag leaf area QFLA-XX.5D.2,QFLA-ZX.2B and QFLA-ZX.4B.1.7.This study found that QTLs for yield-related traits had one-cause pleiotropic or QTL clustered distribution on 21 chromosomes of wheat.A total of 85 single-cause pleiotropic loci were located in the two populations.49 QTL clusters were located in Xinong 1376 / Xiaoyan 81 population.A pleiotropic QTL that control spike length spike density and flag leaf width was detected on 2D chromosome,located in the interval of AX-111561744~AX-179557748,with a contribution rate of 19.62%~50.44%.This locus can be detected in 7 environments and is a stable main effect QTL;One factorial multiple effect QTL controlling spike length,total spikelet number per spike,spike density,thousand grain weight,grain width,flag leaf length and flag leaf width was mapped on 4D chromosome,which was stable QTL;one factorial multiple effect QTL controlling sterile spikelet number per spike,grain number per spike,spikelet fertility,grain number per fertile spikelet,grain length and grain width was mapped on 5A chromosome,which was stable QTL;The univariate multiple effect QTLs for spike length,total spikelet number per spike,spike density,fertile spikelet number per spike,grain number per fertile spikelet,grain length,grain width,flag leaf length,flag leaf width and flag leaf area detected in the 5D chromosome region AX-110220844~AX-109801629 were closely linked with vernalization gene VRN1,which might be a new stable major QTL;One-factor pleiotropic QTL that controls total spikelet number per spike,spike density,fertile spikelet number per spike and grain length are located on chromosome 7A,which is a stable QTL.36 unigenic multiple effect loci were identified in Zhoumai 8425 b / Xiaoyan 81 population.The unigenic multiple effect QTL controlling spikelet number,fertile spikelet number and grain number per spike detected on chromosome 2B accounted for 15.53%,which was a stable major effect QTL;The one-cause pleiotropic QTLs detected on the 5A chromosome that control sterile spikelet number per spike,grain number per spike,spikelet fertility,and grain number per fertile spikelet,with a contribution rate of 14.63%,and are stable major QTLs;The one-cause pleiotropic QTLs detected on chromosome 6A that control spike length,total spikelet number per spike,fertile spikelet number per spike,grain number per spike,thousand grain weight,grain length,grain width and flag leaf length,with a contribution rate of 15.49%,and are stable main effect QTLs;The one-cause pleiotropic QTLs detected on the 7A chromosome that control total spikelet number per spike,spike density,fertile spikelet number per spike,sterile spikelet number per spike,spikelet fertility and grain number per fertile spikelet,with a contribution rate of 16.28%,which is stable Main effect QTL.