Identification, diversity and population structure of Hymenoscyphus fraxineus infecting Fraxinus in Europe

The objective of WP3 is to develop genetic information on the new emerging pathogens and define the genetic structure of the pathogen populations. Particularly, the TASK 3e aims to elucidate the genetic structure of the invasive plant pathogen Hymenoscypus fraxineus (Hf) in EU. Hymenoscypus fraxineus is one of the most recent invading, highly destructive tree pathogens in Europe. This ascomycete causes a lethal fungal disease leading to the massive dieback of European common ash Fraxinus excelsior endangering this widespread keystone species of European riparian ecosystems (Pautasso et al. 2013; McKinney et al. 2014). The disease was first observed in the early 1990s in Poland and subsequently spread with enormous speed to numerous European countries (Timmermann et al. 2011; Pautasso et al. 2013). Recently, the epidemic’s front reached the UK and Ireland (DEFRA 2013), and it is assumed that it is a matter of time before the major natural distribution range of common ash in Europe will be affected (Gross et al., 2014). Of key importance is to understand the population genetics within the old invaded and new areas of expansion to potentially make inferences of introduction events, the number of introduced genotypes, or the identification of invasion routes (Grünwald and Gross, 2012).