Development Of Wheat Single Segment Substitution Lines For Agronomic Important Traits And Fine Mapping Of Major QTLs Controlling Heading Date

Common wheat genotype Laizhou953, wheat genotype Am3 synthesized by crossing Triticum carthlicum (AABB) with Aegilops tauschii (DD), 14 introgression lines (ILs) derived from the BC4F4 generation of Laizhou (recurrent parent)/Am3, 14 F2 populations using the 14 introgression lines to cross with Laizhou953 and parts of the F3 families were used as materials to carried out investigation of 8 agronomy traits, SSR detection and fine mapping of QTLs (quantitative trait loci) controlling heading date (HD). Results were obtained as below:1. 8 agronomic important traits of Laizhou 953 and 14 introgression lines were investigated, and the significance of differences of every trait between each introgression line and Laizhou953 was detected using t-test. The results showed that each introgression line had 2-7 traits showing significant difference from Laizhou953. For every trait, there were positive effects from Am3.2. 500 pairs of wheat SSR markers were used to detected polymorphism between Laizhou953 and Am3, in which 436 pairs of them amplified stable PCR products and 143 pairs showed polymorphism between the two parents. Among them, 112 pairs mapped in the wheat SSR consensus linkage map were used to detect the introgressed segment from Am3 in the 14 introgression lines and 54 pairs detected 101 homozygous segments of Am3 with average length of 16.64cM and 13 heterozygous segments of Am3 with average length of 8.69cM. Each introgression line contained 3-15 homozygous introgressed segments with average number of 7.21 and average length of 12.28cM and 0-4 heterozygous introgressed segments with average number of 0.93 and average length of 4.7cM. Among 14 introgression lines, IL-1 had the most introgressed segments of 15, while IL-6 and IL-8 were the least of 3, respectively. The ratio of coverage of the recipient genome ranged from 1.7% of IL-13 to 14.2% of IL-1 and in average of 7.48%.3. 10 F2 populations using 10 of the 14 introgression lines to cross with Laizhou953 and parts of F3 families were used to select single segment substitution lines (SSSLs), 40 Am3 segments were detected and 22 single segment substitution lines (SSSLs) contained only one homozygous or heterozygous donor segment were selected from F2 populations, and 4 from F3 families. The 26 single segment substitution lines represent 15 different donor segments which have high value in the detection and fine mapping of wheat QTLs.4. Heading date of 11 F2 populations obtained by crossing the introgression lines parents (IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-9, IL-10, IL-12, IL-13, IL-14) which showed significant difference with Laizhou953 were investigated and the heading date were further tested by the F3 families, the distribution of 3 (IL-14/Laizhou953, IL-10/Laizhou953, IL-13/Laizhou953) populations showed classical bimodal distribution.χ2 (Chi square) tests showed that heading date segregate according to the 3:1 ratio which indicated that heading date in the 3 introgression lines has been dissected into single Mendelian factor and can be mapped as qualitative trait.5. Two extreme type (heading earlier and heading later) individual plants and the segregation of the polymorphic markers in the populations were used to detect the relationship between markers and heading date. The markers concerned to heading date were detected and were used to map the QTL using the three populations. In the population of IL-14/Laizhou953, heading date links with 3 co-dominant SSR markers Xgwm261, Xgwm455 and Xgwm484 with the genetic distances of 17.7cM, 23.5cM and 15.4cM, respectively, the locus was temporarily named as Qhd-D1. In the population of IL-10/Laizhou 953, only one co-dominant marker Xgwm484 linked with the heading date locus with the genetic distance of 10.2cM and was temporarily named as Qhd-D2. Because the marker Xgwm484 was located on the chromosome 2D, the two loci were probably the same locus. In the population of IL-13/Laizhou953, heading date was only linked with one dominant marker Xgwm455 with the genetic distance of 4.1cM and was temporarilly designated as Qhd-A1.