High Density Mapping of Powdery Mildew Resistance Gene Qpm.Tut-4A Introgressed to Bread Wheat from Triticum militinae

Powdery mildew is one of the most deleterious wheat diseases caused by fungal pathogen Blumeria graminis f. sp. tritici. Recently, a race nonspecific resistance locus QPm.tut-4A effective during seedling and adult plant stage was introgressed from T. militinae to the 4AL chromosome arm of bread wheat cv. Tähti, creating resistant introgression line 8.1. In effort to clone the gene, two high-resolution mapping populations were created and advanced wheat genomic resources were employed for efficient marker development. The survey sequences of 4AL arm of cv. Chinese Spring and the same arm carrying T. militinae introgression together with 4A GenomeZipper were used. The mapping population originating after crossing susceptible cv. Chinese Spring with the line 8.1 comprises 7500 lines and using 51 new molecular markers, the QPm.tut-4A gene region was delimited to 0.013 cM. Moreover, two recombination hotspots flanking the region were discovered. The second mapping population was derived from cross of the line 8.1 and cv. Chinese Spring with homozygous ph1^- gene. Among 1256 lines of this population, about 27 fold higher recombination rate was observed and the QPm.tut-4A gene region was divided by another four recombination events. The locus was anchored to the Chinese Spring 4A chromosome-specific physical map and BAC clones spanning the region will be used to identify QPm.tut-4A candidate genes. This work has been supported by grant LO1204 from the National Program of Sustainability I, by the Czech Science Foundation (14-07164S) and by Estonian Ministry of Agriculture.