Hymenoscyphus pseudoalbidus, the causal agent of European ash dieback. (7th October 2013)

• Record Type: Journal Article
• Authors: Gross, Andrin; Holdenrieder, Ottmar; Pautasso, Marco; Queloz, Valentin; Sieber, Thomas Niklaus
• Is Part Of: Molecular plant pathology. Volume 15:Number 1(2014:Jan.)
• Page Start: 5
• Page End: 21
• Publication Date: 2013-10-07
• Subjects: Plant diseases -- Molecular aspects -- Periodicals; Plant-pathogen relationships -- Molecular aspects -- Periodicals; 571.936
• DOI: 10.1111/mpp.12073
• Languages: English
• ISSNs: 1464-6722

Abstract

<abstract abstract-type="main"> <title>Summary</title> <sec id="mpp12073-sec-1001" sec-type="section"> <p>The ascomycete <italic>Hymenoscyphus pseudoalbidus</italic> (anamorph <italic>Chalara fraxinea</italic>) causes a lethal disease known as ash dieback on <italic>Fraxinus excelsior</italic> and <italic>Fraxinus angustifolia</italic> in Europe. The pathogen was probably introduced from East Asia and the disease emerged in Poland in the early 1990s; the subsequent epidemic is spreading to the entire native distribution range of the host trees. This pathogen profile represents a comprehensive review of the state of research from the discovery of the pathogen and points out knowledge gaps and research needs.</p> </sec> <sec id="mpp12073-sec-0001" sec-type="section"> <title>Taxonomy</title> <p>Members of the genus <italic>Hymenoscyphus</italic> (Helotiales, Leotiomycetidae, Leotiomycetes, Ascomycota) are small discomycetes which form their ascomata on dead plant material. A phylogeny based on the internal transcribed spacers (ITSs) of the rDNA indicated the avirulent <italic>Hymenoscyphus albidus</italic>, a species native to Europe, as the closest relative of <italic>H. pseudoalbidus</italic>.</p> </sec> <sec id="mpp12073-sec-0002" sec-type="section"> <title>Symptoms</title> <p> <italic>Hymenoscyphus pseudoalbidus</italic> causes necrotic lesions on leaves, twigs and stems, eventually leading to wilting and dieback of girdled shoots. Bark lesions are characterized by a typical dark‐ to cinnamon‐brown discoloration.</p> </sec> <sec id="mpp12073-sec-0003" sec-type="section"> <title>Life cycle</title> <p> <italic>Hymenoscyphus pseudoalbidus</italic> is heterothallic and reproduces sexually on ash petioles in the litter once a year. Ascospores are wind dispersed and infect ash leaves during the summer. The asexual spores only serve as spermatia.</p> </sec> <sec id="mpp12073-sec-0004" sec-type="section"> <title>Tools and techniques</title> <p>The most important techniques for fungal handling, such as detection, isolation, culturing, storage, crossing and ascocarp production, are briefly described.</p> </sec> <sec id="mpp12073-sec-0005" sec-type="section"> <title>Management</title> <p>Once the disease is established, management is hardly possible. The occurrence of a small fraction of partially tolerant trees constitutes hope for resistance breeding in the future. Healthy‐looking trees should be preserved.</p> </sec> </abstract>