QTL Mapping And Meta-analysis For Spike-related Traits In Wheat(Triticum Aestivum L.)

The spikelet number per spike,the kernel number per spike and productive tiller number are mportant components of wheat(Triticum aestitum L.)yield.However,under drought stress conditions,wheat reduced the spikelet number per spike,the kernel number per spike and productive tiller number to alleviate the injury of drought stress on the plant,maximize to maintain survival and produce offspring.And they showed significant flexible adaptation to water and generally low heritability,which were complex quantitative traits controlled by polygenes.So it is critical to explore the main effective quantitative trait loci(QTL)and its closely linked molecular markers by the molecular quantitative genetics and metaanalysis in molecular improvement in wheat.The efficiency and accuracy of genetic improvement of related traits are of great significance.In this study,a total of 120 recombinant inbred lines(RILs)derived from Chinese winter wheat cultivars Longjian19×Q9086 and the two parents were taken as test materials,setting different water environment,to do the QTL mapping and molecular quantitative genetic analysis for the spikelet number per spike,the kernel number per spike and the productive tiller number.Then integrating the QTLs information,the meta-analysis is performed,to explore the meta QTLs and their closely linked molecular markers.The research results are as follows:1.The spikelet number per spike,the kernel number per spike and productive tiller number in wheat RIL population are sensitive to water stress,and generally show low heritability(0.44~0.71).The strains in the population are wide variations and transgressive segregations.And they were complex quantitative traits controlled by polygenes.2.According to the different spike-related traits of wheat,a total of 22(the productive tiller number)~43(the kernel number per spike)addictive QTLs(A-QTL)and 22~84 pairs epistasis QTLs(AAQTL)were detected.These sites are distributed on all 21 chromosomes of wheat,accounting for phenotypic variations of 0.14~11.87% and 0.02~3.91%,respectively.All detected A-QTLs interacted with the water environment,0.32~6.83% and 0.11~9.2% by AA-QTL interactions with water environments.These QTL and their genetic effects interacting with the water environment showed positive and negative regulation to phenotypic variations in spike-related traits.3.Some QTLs,such as QSns.acs-2A.1,QKns.acs-2A.2,QKns.acs-5B.1 and QPtn.acs-7B.1 were repeatedly detected in multi-environments on chromosomes 2A,5B and 7B.In addition,6 A-QTL hot-spot regions were also found in some specific intervals.Among them,the marker interval Xgdm645~Xwmc529 on chromosome 3D,Xgwm165~Xmag1353on chromosome 4A,Xwmc621~Xba rc107 on chromosome 6A,Xksum153~Xwmc607 on chromosome7 A,Xmag353~Xwmc517 on chromosome 7B and Xwmc634~Xbarc76 on chromosome 7D.4.To explore true and major QTLs,a total of 365 QTLs controlling spike-related traits from different genetic populations in wheat were employed to establish consensus map and to perform meta-analysis by the method of bioinformatics,depending on a high-density genetic map as a refer ence map.35 of meta QTLs(MQTL)for the spikelet number per spike,33 of MQTLs for the ke rnel number per spike and 24 of MQTLs for the productive tiller number,the confidence interval can be reduced to 0.55 cM,which makes the QTLs become more accurate and reliable.the distribution of MQTLs was enriched and cluster on the specific intervals.Among them,the marker inter val XksuG2~Xgdm111 on chromosome 1D,Xgwm312~Xsrap29a on chromosome 2A,Xwmc18~Xg wm157 on chromosome 2D,Xswes147~Xgwm180 on chromosome 4A,Xgwm644~Xwmc269.3 on chromosome 6B and Xswes625~Xgem526 on chromosome 7B.The MQTLs of these segments wer e located in the same or overlapping area,which indicated many important genes controlled the sp ike-related traits could locate on these key marker intervals and it could exist “pleiotropism” sites.5.The study was identified 8 candidate genes on the “consensus” QTLs of the spike-related t raits by physical location and comparing these sequences with other genes by software.In this study,the phenotypic variation characteristics of spike-related traits in the RILs population were studied by setting up multiple water environment,and the genetic basis was clarified.The candidate genes,stable expression QTLs and meta QTLs were explored,and the hot-spot regions would provides theoretical and technical basis for the molecular genetic improvement in drought resistance.