European Journal of Plant Pathology (2011) 130, 311-324

Claude Husson, Bruno Scala, Olivier Caël, Pascal Frey, Nicolas Feau, Renaud Ioos and Benoît Marçais (2011)
Chalara fraxinea is an invasive pathogen in France
European Journal of Plant Pathology 130 (3), 311-324
Abstract: Decline induced by Chalara fraxinea is an emerging disease that severely affects ash stands in Europe. The disease appears to have an invasive spread from East to West of Europe in the last decade. The teleomorphic stage, Hymenoscyphus pseudoalbidus, that occurs as apothecia on ash rachis in the litter was recently described. The origin of ash decline remains unclear as a cryptic species, H. albidus, a long-established fungus in Europe, could be present in the same niche, and as in Switzerland, H. pseudoalbidus was shown to have been present long before the recent epidemic outbreak. In France, the emerging disease is very recent and clearly restrained to Northeastern France. We thus collected isolates from infected hosts and from apothecia/ash rachis both inside and outside the infected area in France in order to compare them on the basis of pathogenicity towards ash seedlings and sequences of the ITS regions and of three single-copy genes. We showed that two population types exhibiting about 2% base pair polymorphism in the sequences analysed were present in Northern France. The first type, corresponding to H. pseudoalbidus, was present on rachis and infected hosts only in Northeastern France and showed strong pathogenicity towards ash seedlings in inoculation tests. By contrast, the second type, which corresponds to H. albidus, was present throughout Northern France and showed no pathogenicity towards ash seedlings. Our study confirms the results of Queloz et al. (2010) who presented molecular evidences for the existence of two cryptic species, H. albidus and H. pseudoalbidus. The results strongly suggest that Chalara fraxinea/H. pseudoalbidus is a recent invader in France.
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Link to article at publishers website
Database assignments for author(s): Pascal Frey, Benoit Marçais, Renaud Ioos

Research topic(s) for pests/diseases/weeds:
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Hymenoscyphus fraxineus	Ash (Fraxinus)	France
	Hymenoscyphus albidus		France