Most fungi are able to undergo both asexual (clonal) and sexual reproduction. A predominance of asexual reproduction is frequently observed in invasive fungal plant pathogens at the beginning of an epidemic in a newly invaded area. Over time, in clonally reproducing genotypes novel genotypes may arise through mutations, resulting in clonal lineages. These may be highly successful, colonize large parts of the introduced range of the pathogen, and persist over years. In this project, we will investigate the molecular epidemiology of clonal lineages of the invasive pathogenic fungus Cryphonectria parasitica, the causal agent of chestnut blight. For this, we will rely on genome-wide SNPs that we will detect by conducting whole-genome resequencing of a high number of isolates from different geographic populations.