Abstract
Every year, fungal diseases cause over 138 million tons of wheat yield loss, among them the powdery mildew causing biotrophic ascomycete Blumeria graminis f. sp. tritici. A sustainable approach to combat this disease is the deployment of resistant wheat cultivars. Over 90 powdery mildew resistance genes are known, however, the constant arms race with the rapidly evolving pathogen makes new sources of resistance necessary. Exploiting genetic diversity in older wheat germplasm can provide such resistance sources. Here, we assembled a diverse collection of 755 bread wheat accessions with a focus on landraces based on geographical origin and powdery mildew resistance phenotypes. Genotyping the panel revealed higher genetic diversity in landraces compared to cultivars and currently available high-quality sequenced genomes. Genome-wide association studies detected 22 seedling stage resistance-associated loci that represent a new source of genetic resistance. Further reduction of the panel to 281 accessions facilitated adult plant resistance assessment in the field. We present seven wheat accessions with stable adult plant resistance across five tested environments and a potential QTL QPm.lpww-2DL on chromosome 2DL that is associated with adult plant resistance. In conclusion, this thesis contributes to unlocking the value of bread wheat landraces for powdery mildew resistance breeding.
Leber, Rebecca