Genome sequencing of several strains of the ash dieback pathogen Hymenoscyphus fraxineus

Ash dieback caused by Hymenoscyphus fraxineus (previously known as H. pseudoalbidus; anamorph Chalara fraxinea) is now reported in about 200 sites in the UK. Ash (Fraxinus excelsior L.) is a common hedgerow tree widely planted for amenity and forestry purposes. It makes up 5.4% of British woodland. Ash dieback will alter woodland structure and rural landscapes, and cause losses of amenity trees, commercial plantations and breeding programmes. Indirect consequences include loss of ash-associated fauna and epiphytes and opening of woodland canopies with impacts on ground flora and fauna, nutrient flush, litter breakdown and carbon sequestration. The NORNEX consortium aims to acquire rapidly a high level of understanding of the pathogenicity of the fungus and genetics of resistance in the host. This knowledge will underpin the development of rational strategies for control and mitigation of the effects of the disease in the field, through both control of fungal spread and discovery of resistant ash genotypes for rapid repopulation. H. fraxineus is a recent introduction into Europe from Asia. In collaboration with colleagues across Europe, we are sequencing the genomes of a wide range of H. fraxineus isolates from Europe to understand the population biology of the fungus, its relationships to Asian H. fraxineus, and its relationships to other Hymenoscyphus species. The chosen isolates span the full geographical range of the current epidemic as well as capturing the temporal spread of the fungus since its introduction. The assembled genomes and the genes predicted from them may also inform research into infection cycles, pathogenicity and control strategies for this invasive fungal pest.