Development Of NIILs And Mapping Of Major QTLs Related To Yield In Wheat

Common wheat genotype Laizhou953, wheat genotype Am3 synthesized by crossing Triticum carthlicum (AABB) with Aegilops tauschii (DD), 8 intro -gression lines (ILs) derived from the BC4F4 generation of Laizhou (recurrent parent)/Am3, 2 F2 populations using the 2 introgression lines (IL15, IL16) to cross with Laizhou953 and the F3 families were used as materials to carried out SSR detection of the introgressed donor segments, investigation of 4 traits related to yield, and mapping of major QTLs (quantitative trait loci) related to yield. Results were obtained as below:1. 957 pairs of wheat SSR markers were used to detected polymorphism between Laizhou953 and Am3, in which 793 pairs of them amplified stable PCR products and 241 pairs showed polymorphism between the two parents, the frequency of polymorphic markers was 30.4%. Among the polymorphic markers, 83 markers were located on the linkage groups and 72 of them detect -ed introgressed segements of Am3 in the 8 introgression lines. Totally,115 donor segements with average length of 11.4 cM, covering 11.4% of the total of genome were detected. Among 8 introgression lines, IL21 had the most introgression segements of 27, while IL17 were the least of 7, respectively. IL21 had the longestest ingression segements with average length of 17.6cM, while IL-20 was the shortest with the length of 9.55 cM. IL-21 showed the highest coverage of donor introgression (25.3%), while IL17 and IL20 were the lowest (5.2%).2. Four traits, the spikes per plant, spike length, grains number per spike, spikelets of Laizhou 953 and 2 introgression lines were investigated. The results showed that the 4 traits of the 2 introgression lines had significant difference from Laizhou953. Compared with Laizhou953, the two introgre ssion lines showed shorter spike length, fewer grains number per spike and spikelets, but more spikes per plant. Correlation analysis indicated that the performance value of 4 traits showed high correlation (0.57~0.72), spikes per plant and other 3 traits had an obvious negative correlation (-0.57~-0.71).3. The spikes per plant, spike length, grains number per spike and spike -lets of IL15/Laizhou953 and IL16/Laizhou953 F2 and F3 families were investi -gated. The results showed that 4 traits segregated significantly, in the popula -tion of IL16/Laizhou953, 4 traits had shown a clear bimodal distri bution. According to the traits of F3 families we deduced the corre spon ding F2 genetype, and analyzed the segregation of F2 populations.χ2 (Chi square) tests showed that 4 traits segregate according to the 3:1 ratio which indicated that QTLs of 4 traits have been dissected into single Mendelian factor and can be mapped as qualitative trait loci in this population.4. Two extreme types of individual plants of 4 traits in the population were used to study the relationship between the introgressed donor segment and phenotype. It was showed that 3 SSR makers Xgwm513, Xwmc657 and Xgwm495 located on 4B showed high correlation with 4 traits and were run across the population. A linkage group was constructed with a total genetic distance of 16.59 cM. A F2:3 model and software proposed by Zhu et al. (2007) was used to analyze the phenotype data of this population to ascertain the position of the QTLs in this linkage group, and the four QTLs were all located to the position of 12.9 cM in this linkage group between marker Xwmc657 and Xgwm495. Therefore, the four QTLs designed as Qspp-am3, Qsl-am3, Qspi-am3, Qgps-am3 were controlled by one locus. The linkage of this region was constructed which was coincide with the 4B linkage map of Somer et al. (2004). Mapping of the QTLs related to yield as Mendalian factors lay a foundation for the fine mapping of this region for the map-based cloning and marker assist selection in breeding program.