Identification and characterisation of genes underlying host specificity/non host resistance in the wheat powdery mildew pathosystem

• Applicant: Dr. Marion Müller
• Subject Area: Plant Breeding and Plant Pathology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 543878450

Plant pathogenic fungi with a biotrophic lifestyle often display a high level of host specificity, restricting their ability of infection to only a single or a very limited number of host species. Importantly, host specificity and non-host resistance on the plant side are not static but they can evolve over time. Such shifts in host ranges can lead to the emergence of devastating new agricultural diseases. As a result, gaining a deeper understanding of the related processes is of high importance for resistance breeding. In this project, our primary objective is to identify and characterise the genetic factors that underlie both host specificity and non-host resistance, using wheat (Triticum ssp.) and the powdery mildew pathogen (Blumeria graminis) as a model system. Wheat (Triticum spp.) serves as a host to two distinct fungal formae speciales of Blumeria graminis: one specializing on domesticated hexaploid wheat (B.g. f.sp. tritici, Bgt) and the other on wild tetraploid wheat (B.g. f.sp. dicocci, Bgdic). It was proposed that polyploidization and subsequent domestication between Aegilops tauschii and a tetraploid wheat progenitor, which resulted in the formation of hexaploid wheat, represent the events leading to the separation of these two wheat-infecting lineages. Consequently, we hypothesise that the D subgenome of hexaploid wheat (originating from Ae. tauschii) harbors genetic factors that impede the colonization of hexaploid wheat by Bgdic. Our project aims to isolate and identify these factors using a combination of approaches, including genome-wide association studies in an Ae. tauschii diversity panel and map-based cloning. In parallel, we will utilize our newly developed fungal avirulence depletion assay that combines experimental crosses with artificial selection and bulk-segregant analysis. This approach will allow us to rapidly identify the genes responsible for determining host specificity in wheat powdery mildew. Upon successful candidate gene identification on both the fungal and plant side, we will proceed with functional validation and characterization of these genes using state-of-the art experimental techniques. In combination with diversity analysis, this project will provide novel insights into the dynamic evolution of host specificity and non-host resistance genes in both the fungus and the plant and thereby offer unprecedented insights into the emergence of new fungal lineages with altered host ranges.

• DFG Programme: Research Grants