Molecular Marker Of Wheat Powdery Mildew Resistance Genes And Multi-genes Pyramiding Marker-assisted Selection

Powdery mildew, caused by Erysiphe graminis f.sp tritici, is a destructivedisease of common wheat throughout the world. Breeding and popularizingresistance cultivars has been proved the most effective, economical andenvironmentally safe method to suppress the pathogen. However, theresistance cultivars containing single Pm gene often loss the resistancebecause of the pressure from the powdery mildew pathogen's dissociation. Sobreeding pyramiding cultivars containing 2 or 3 or more Pm genes using themolecular MAS strategy, including Pm gene's marking and location is anurgent task. 1. The powdery mildew resistance gene Pm18 is immune to the presentdominant pathogens. In this study, Bulked segregant analysis (BSA) was usedto search for RAPD markers linked to this gene. 350 decamer primers werescreened and one RAPD marker (S411600) linked to Pm18 was identified. Theanalysis to the F2 mapping population from a cross of Pm18 (resistant parent)×Chancellor (susceptible parent) indicated that the marker S411600 wasco-segregating with the gene Pm18. This conclusion was further validated bythe analysis to the testing population, the F2 population from a cross of Pm18(resistant parent) ×Mingxian169 (susceptible parent). This marker, which isthe first co-segregating RAPD marker of the gene Pm18, can be convenientlyused for marker-assisted selection in wheat breeding programs for theidentification or pyramiding of Pm18. 2. The Pm23 is also an excellent powdery mildew resistance gene, which isimmune to the present dominant pathogens and had been located in the 5Achromosome. Bulked segregant analysis (BSA) was used to search for RAPD 3小麦抗白粉病基因的分子标记及多基因聚合体的分子标记辅助选择and SSR markers linked to Pm23 gene. 350 decamer primers and 97(18 ofthem locates in 5A chromosome) SSR primers were screened and one RAPDmarker (OPE051100) closely linked to Pm23 had been identified; and no SSRmarker linked to Pm23 had been found. The analysis to the F2 mappingpopulation from a cross of Pm23 (resistant parent) ×Chancellor (susceptibleparent) indicated that the marker OPE051100 was linked to Pm23 at a geneticdistance of 10±3.2cM. By now, no markers linked to Pm23 have been reported.The marker OPE051100 is the first marker of the gene Pm23 and it can beconveniently used for marker-assisted selection in wheat breeding programsfor the identification or pyramiding of Pm23. 3. Using the RAPD markers linked to Pm18 and Pm23 we identified andthe STS marker(Pm4b-STS410) linked to Pm4b previously reported, combiningwith the strategy of selecting and planting resistant plants by inoculating andobserving in earlier generation, RAPD and STS marker-assisted selectingresistant plants in F3, 3 pyramiding plants containing Pm4b+Pm18, 5pyramiding plants containing Pm4b+Pm23, 2 pyramiding plants containingPm18+Pm23 were selected from the resistant progenies of the hybridizationassembles (Pm4b×Pm23) × (Pm19×Pm18). And the pyramiding plants, whichare immune to the wheat powdery mildew and characterized by goodagronomy, can be used as excellent germ plasm in wheat powdery mildewresistance breeding. The results showed that MAS pyramiding breeding cannot only break the linkage encumbrance of bad genes existing in the linescontaining these Pm genes, but also ease labor and increase the efficiency ofselection in wheat breeding program.