Structural Variations of T. militinae Locus Introgressed into Wheat Chromosome Arm 4AL and Conferring Improved Powdery Mildew Resistance

Gene pool of bread wheat has been narrowed down by intensive breeding which limits the palette of agronomically important genes. Introgression of genome segments from related species is promising way to overcome this limitation. However, differences in genome structure accumulated during evolution of the relative species may hamper successful implementation of introgressions into breeding process. QPm.tut-4A powdery mildew resistance locus was introgressed into bread wheat from T. militinae. The large scale synteny in the region was well preserved between cv. Chinese Spring (CS) and the donor. However, the fine-mapped owm169 – owm228 gene region represented by 640 kbp of CS genomic sequence shows major sequence differentiation from T. militinae. Only 7.9% of compared sequences close to flanking markers show high identity (<90%). The T. militinae region comprises about 3 % more repetitive elements and accumulated 15.3 % more families of transposable elements. On the other hand, the regions comprise about the same amount of predicted protein coding genes excluding genes of transposable elements. The observed sequence divergence is most likely responsible for inhibition of recombination in the locus and represents challenge for identification of the QPm.tut-4A candidate gene. 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.