| Aegilops tauschii Cosson（DD,2n=2x=14）,the wild relatives of common wheat,containsbeneficial genes such as insect resistance.disease resistance and abiotic resistance,the excellent genes of Ae.tauschii can be introduced into common wheat by means of distant hybridization methods,is considered as a prospective genetic resource for improving common wheat.This study was using Aegilops tauschii T093 and Zhoumai 18 hybridization directly,which were treated with colchicine to generate synthetic octaploid wheat.The next year,emasculated florets of Zhoumai 18 were pollinated by synthetic octaploid wheat to generate BC1F1 seeds.Afterwards,the BC1F1 plants,as female parents were successively backcrossed two times by Zhoumai 18 and then selfed six generations to produce advanced backcrossed population（BC3F6population）.After investigation of the agronomic traits of Huixian and Zhongmu in 2015-2016,the genotype data of SSR molecular marker and QTL IciMapping V4.0 software according to the phenotypic data of BC1F7 substitution line,and the days to heading,days to flowering,spike length,plant height,spikelets,thousand kernel weight,grain perimeter,grain length,grain width and spikelet density were used for QTL mapping.The following results are obtained:（1）Polymorphism marker on the D genome and the number of introgressed segments three hundred and twelve BC3F6 line was successfully genotyped by SSR markers.Altogether 1114 SSR markers were used to detect polymorphism between the donor parent Ae.tauschii T093 and the recurrent parent Zhuomai 18.Among them,polymorphism between the two parents was detected in 374 SSR markers,and121 of them were confirmed to be polymorphic in the BC3F4 advanced backcross population.After using121 polymorphic primers to detect BC3F6 chromosome fragment substitution population,76 of them were confirmed to be polymorphic in the advanced backcross population,accounting for 62.8%,with an average of 10.8 markers for each chromosome.Most of the polymorphic markers were observed on chromosome5D with the total number of 29,whereas the least was found on chromosome 1D with the total number of only 3.Besides the unidentified 70 markers,a physical map was constructed based on the 304 polymorphic SSR markers between parents,which displayed heterogeneous distribution on 7 linkage groups of D genome,with a total length of 4004.5 Mb.The physical map illustrates an average interval of 36.2 Mb among 76 polymorphic markers in the population,while these markers also exhibit inhomogeneous distribution in different chromosome regions.（2）According to the physical positions of SSR markers,the size of each introgressed segment in the lines and ratios accounting for the whole donor genome were estimated.The introgressed segments range from 1.0 to 60.5 Mb.There were a total of 76 polymorphic markers on the entire genome,a total of1369 homozygous fragments were introduced and the average length was 9.4 Mb.There were 299heterozygous fragments and an average length of 10.9 Mb,and the maximum coverage rate was 20.8%.（3）The phenotypic variation analysis of BC3F6 substitution line population in the two environments of Huixian and Zhongmu found that,the range of trait variation between BC3F6 substitution line population is larger,the coefficient of variation in Huixian County is 0.493-7.531%,while that in Zhongmu County is 0.729-16.060%.there is a clear phenomenon of separation of super-parents（recurrent parent Zhou Mai 18）in this group.The absolute value of the skewness and kurtosis of most traits are less than 1,the frequency distribution shows a normal distribution,which is continuous variation;it shows that the 10 phenotypic traits of the BC3F6 substitution line are all quantitative traits.All of these traits meet the criteria for genetic effect analysis and QTL mapping.（4）The QTLs were mapped to the BC3F6 substitution lineage population in Huixian County and Zhongmu County,sixteen additive QTLs were located,they were located in the six traits:days to heading,days to flowering,spike length,plant height,spikelets,thousand kernel weight,grain perimeter,grain length,grain width and spikelet density,in addition,an additive QTL locus was also mapped in the trait of grain width in Zhongmu.These additive QTL loci are located on the 1D,2D,3D,5D,6D and 7D chromosomes.Specifically,in Huixian BC3F6 substitution population,three QTL loci associated with days to heading were located on chromosome 2D,3D and 6D chromosomes;two QTL loci associated with days to flowering were located on 2D and 6D chromosomes;three QTL loci associated with spike length were located on 1D and 2D chromosomes;two QTL loci associated with plant height were located on 2D and 6D chromosomes;three QTL loci associated with spikelets were located on 3D,5D and 7D chromosomes;three QTL loci associated with spikelet density were located on 2D,5D and 6D chromosomes.In Zhongmu BC3F6 substitution population,two QTL loci associated with days to heading were located on chromosome2D and 6D chromosome;two QTL loci associated with days to flowering were located on 2D and 3D chromosomes;three QTL loci associated with spike length were located on 1D and 2D chromosomes;two QTL loci associated with plant height were located on 2D and 7D chromosomes;three QTL loci associated with spikelets were located on 3D,5D and 7D chromosomes;one QTL loci associated with grain width were located on 5D chromosomes,three QTL loci associated with spikelet density were located on 2D and6D chromosomes. |
