Construction And Molecular Characterization Of Chromosome D Segment Substitution Lines In Synthetic Hexaploid Wheat

Some wheat yield traits, such as the number of tillers, the number spikelet of main spike, the number of grain per spike and thouthend-grain weight, are quantitative traits, which are vulnerable to environment. Therefore, there are strong genetic and environmental interactions on these quantitative traits. The accurate identification and mapping quantitative trait loci are the basis of molecular marker-assisted selection for breeding and map-based gene cloning. Developing the chromosome segment introgression lines could not only develop and use the new gene resource, greatly improve veracity and accuracy of QTL mapping, but also make those discontinous segments (identiy of gene, gene mapping, gene expression analysis, maker-assisted slection and breeding) together. Single segment substitution lines (SSSLs) is an ideal material for genetic analysis and QTL analysis. Therefor, it is very important for the establishment of the single segment substitution lines. Crossing Aegilops tauschii AS60(,DD,2n=14) with Chinese unique turgidum wheat AS2255(T. turgidum L. ssp. turgidum, AABB,2n=28), a synthetic hexaploid wheat line SHW-Ll (AABBDD,2n=42) was obtained. A total of171F8recombinant inbred lines were developed by crossing Chuanmai32with SHW-Ll, and a genetic linkage map was developed by SSR markers. Through backcross and molecular marker-assisted selection, a set of D genome introgression lines of synthetic hexaploid wheat was created. 1. A SSR genetic linkage map of D genome was obtained by using F8recombinant inbred lines. This genetic map with the length of1696.2cM contained135SSR markers. The length of chromosome1D is319.8cM including25SSR markers. The average length between two markers on chromosome1D is12.8cM. The length of chromosome2D is191.5cM including23SSR markers. The average length between two markers on chromosome2D is8.3cM. The length of chromosome3D is143cM including8SSR markers. The average length between two markers on chromosome3D is18.2cM. The length of chromosome4D is223.4cM with15SSR markers. The average length between two markers on chromosome4D is14.89cM. The length of chromosome5D is273.4cM with15SSR markers. The average length between two markers on chromosome5D is18.2cM. The length of chromosome6D is252.8cM with25SSR markers. The average length between two markers on chromosome6D is12.0cM. The length of chromosome7D is292.0cM with28SSR markers. The average length between two markers on chromosome7D is12.04cM. The average length between two markers on the whole D genome is12.6cM.2. Genetic background of87Fg lines was checked by SSR markers. The number of D genome fragments ranged from7to20in the87F8lines, with the average fragments number of13.9. The fragment length varied from17cM to120cM, with the average of42cM. The genetic background recoverage rate ranged from34.2%to86.6%, with the average of54.8%. The genetic background variation rate varied from1.0%to29.0%, with the average of11.0%.3. The variations of SSR loci on D genome were observed. The variation frequency of each marker on the chromosomes1D-7D ranged from0to50.3%. The locus with higher variation frequency was often clustered togethor. Thus, hot variation regions and conserved regions of chromosome were distinguished. For instance, the chromosomal region of the GDM99D on chromosome7D was the hot variation region. The chromosomal region between the CFD188and CFD188on chromosome7D was conserved regions.4. The genetic backgrounds of21F8lines and164FgBC1progenys of the21F8lines were identified. The average coverage rate of introgressed D chromosome segments was15.9%(homozygous fragment2.5%, heterozygous13.4%). Compared with the F8-generation the average coverage rate of introgressed D chromosome segments was reduced but the genetic background recoverage rate in D genome was increased through backcross.5. A set of link-up chromosome segment introgression lines were constructed by SSR marker-assisted selection. Creating and screening these strains with D genome from Aegilops tauschii (Coss.) provides the materials for developing a set of single segment introgression lines.