PM 7/45(2) Cryphonectria parasitica

Abstract

This Standard describes a diagnostic protocol for Cryphonectria parasitica.1

This Standard should be used in conjunction with PM 7/76 Use of EPPO diagnostic protocols.

Approved in 2004–09. Revised in 2024–08.

Authors and contributors are given in the Acknowledgements section.

Cryphonectria parasitica is a bark-inhabiting fungus causing blight of chestnut (Castanea spp.) and other susceptible tree genera and species (mostly Quercus spp.) (EPPO, 2022a). It is native from Eastern Asia, where it was reported in China, Japan and the Korean peninsula, but by the end of the nineteenth century, the disease spread to North America and was reported in Europe in the late 1930s. There is variation in susceptibility between host tree species. The most susceptible are the American chestnut (Castanea dentata) and the European chestnut (Castanea sativa). The virulent form of the disease develops quickly in these species causing necrosis of bark and mortality of the distal part of the tree (Heiniger & Rigling, 1994). Hypovirulence due to infection of the fungus by the RNA virus, Cryphonectria hypovirus 1 (CHV 1), has however, enabled the regrowth of chestnut trees and stands in many regions of Europe. Virulent and hypovirulent strains of the fungus give rise to different types of cankers and this may, in some cases, make detection and identification difficult. In more tolerant hosts (in Europe, mostly Quercus petraea and less often Quercus robur, Quercus ilex and other oaks, as well as hybrids between the European chestnut and Asian chestnut species) or in its hypovirulent form, chestnut blight appears as perennial ‘healing’ cankers with superficial infections of the bark that rarely causes the death of branches, sprouts or the whole tree. Further information on biology and geographical distribution can be found in EFSA (2014) and EPPO (2022a). A datasheet providing more information on the biology is also available in EPPO Global Database EPPO (2022b). See also Fulbright (1999), Heiniger & Rigling (1994), Rigling & Prospero (2018), Roane et al. (1986).

A flow diagram describing the diagnostic procedure for C. parasitica is presented in Figure 1.

Name: Cryphonectria parasitica (Murrill) M.E. Barr.

Other names: Endothia parasitica (Murrill) P.J. Anderson & H.W. Anderson.

Taxonomic position: Fungi: Ascomycota: Diaporthales: Cryphonectriaceae.

EPPO Code: ENDOPA.

Phytosanitary categorization: EPPO A2 list: no. 69, EU PZ Quarantine pest (Annex III) & EU-RNQP (Annex IV).

Host plants may carry the fungus in the bark (to the depth of the cambium).

The fungus can be identified either from its fruiting bodies formed on chestnut or oak cankers or after incubation under moist conditions using morphology and molecular tests or from its growth characteristics in culture after isolation. Distinction of C. parasitica from closely related species requires morphological expertise. Confirmation using a molecular test on mycelium or fruiting bodies is recommended in critical cases or in case of doubt (PM 7/76, EPPO, 2018).

Reference material can be obtained from Westerdijk collection (NL)

ITS reference sequences (e.g. accession numbers EU442645; GU993820) and TEF reference sequences (e.g. KC879168, KP824763) can be found in GenBank.

Guidelines on reporting and documentation are given in EPPO Standard PM 7/77 Documentation and reporting on a diagnosis.

When performance characteristics are available, these are provided with the description of the test. Validation data are also available in the EPPO Database on Diagnostic Expertise (http://dc.eppo.int), and it is recommended to consult this database as additional information may be available there (e.g. more detailed information on analytical specificity, full validation reports, etc.).

Further information on this organism can be obtained from:

Università degli Studi della Tuscia, Dipartimento di Protezione delle Piante, v.s. Camillo de Lellis, I-01100 Viterbo (Italy); E-mail: [email protected]

INRAE, UMR BIOGECO 69, route d'Arcachon 33612 Cestas Cedex; C Robin E-mail: [email protected]

Swiss Federal Research Institute WSL, CH-8903 Birmensdorf (Switzerland); E-mail: [email protected]

If you have any feedback concerning this Diagnostic Protocol, or any of the tests included, or if you can provide additional validation data for tests included in this protocol that you wish to share please contact [email protected].

An annual review process is in place to identify the need for revision of diagnostic protocols. Protocols identified as needing revision are marked as such on the EPPO website.

When errata and corrigenda are in press, this will also be marked on the website.