| As an important food crop in China,the continuous increase in wheat yield is of great significance for ensuring food security.With the swell of population and the decrease of cultivated land,it is curcial to increase wheat yield per unit area to ensure the balance of wheat supply and demand.Wheat yield is a complex character composed of effective spike number per unit area,grain number per spike and grain weight.The number of grain per spike is mainly determined by spike type of wheat,and the grain size directly affects the grain weight.Therefore,it is of great significance to use existing germplasm resources to identify and excavate excellent spike type and grain related loci,and thus developing closely linked molecular markers for genetic improvement and breeding utilization of new varieties with high yeild.Shumai 126 is a new white grain wheat variety with high yield,which has consistently shown excellent yield characteristics in regional and production experiments in Sichuan Province.However,the genetic basis of its high yield remains unclear.To explore the genetic basis of spike and grain closely related to its yield,the Recombinant Inbred Line(RIL)population(TS)was constructed using Shumai 126 as the male parent and the recombinant inbred line(RIL)population of Taichang 29.The genome was scanned by wheat 55 K SNP array to construct genetic map.Combined with the phenotypic data of spikelet type and grain-related traits in multi-year environments,Quantitative Trait Loci(QTL)controlling spikelet length(SL),spikelet number per spike(SNS),spikelet density(SD),as well as wheat grain length(GL),grain width(GW),thousand grain weight(TGW),grain length width ratio(LWR)were identified,and the results were as follows:(1)The spike-type related traits of TS population and its parents were identified in 4environments within 2 years,and the SL and SNS measured data of parent SM126 were significantly higher than those of TC29 in 4 environments.QTL analysis showed that two spikelet QTL could be stably detected in three environments,namely QSL.sicau-TS-6D controlling SL,which explained the phenotypic variation rate of 9.88-13.84%,QSNS.sicau-TS-2D controlling SNS,QSL.sicau-TS-2D controlling SNS,QSL.sicau-TS-2D controlling SL.The phenotypic variation rate of 9.03-10.67% was explained.(2)The grain-related traits of TS population and its parents were identified in 5environments within 3 years,and the GL,GW and TGW of parent SM126 were significantly higher than those of TC29 under 5 environments.QTL analysis showed that the major loci QGW.sicau-TS-1B.1 controlling GW and the major loci QTGW.sicau-TS-1B controlling TGW were stably detected in four environments,explaining 10.00-24.93% and6.86-28.84% of phenotypic variation,respectively.QGW.sicau-TS-1B.1 and QTGW.sicauTS-1B were colocalized on chromosome 1B of wheat,and the physical interval corresponding to the Chinese spring reference genome was 667,641,255-670,373,100 bp,and the interval size was 2.73 Mb.(3)The cross between Shumai 1915(SM1915)and SM126 was used to construct RIL(2SS)as the verification population to verify the accuracy of the markers developed later.The flanking markers of the stable primary locus controlling GW and TGW were transformed into KASP markers,and genotyping and genetic effects were analyzed in TS population and 2SS population.According to the annotation information of Chinese spring reference genome,there were 65 annotated genes in the physical interval of the major loci QGW.sicau-TS-1B.1.Traes CS1B02G448300 was a gene encoding carbohydrate transporter,whose expression regulation affects the formation of grain size,and as the potential candidate gene for QGW.sicau-TS-1B.1.In conclusion,the major QTL identified for yield-related traits,the molecular markers developed and the validated populations constructed in this study laid a good foundation for the analysis of the genetic basis of spike type and grain traits and marker-assisted breeding. |
