Cryphonectria

Fungalpedia – Note 257, Cryphonectria

Cryphonectria (Sacc.) Sacc. & D. Sacc.

Citation when using this entry: Aumentado et al. 2024 (in prep) – Fungalpedia, plant pathogens.

Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig 1.

Classification: Cryphonectriaceae, Diaporthales, Diaporthomycetidae, Sordariomycetes, Pezizomycotina, Ascomycota, Fungi

Cryphonectria belongs to Cryphonectriaceae (Diaporthales) (Gryzenhout et al. 2006a, 2006b), and was established to incorporate Nectria abscondita and N. variicolor, although the type species were not specified (Saccardo & Saccardo 1905, Jiang et al. 2018). Hence, Gryzenhout et al. (2005) proposed Cryphonectria parasitica as the type species of Cryphonectria, which is known to cause chestnut blight. The defining sexual characteristics of Cryphonectria include clustered or solitary, partially embedded, protruding orange ascostromata. The ascostromata are cylindrical-fusoid to club-shaped, attached to pedicels, and contain eight-spored asci exhibiting distinctive refractive J-shaped rings. The ascospores are elliptical, spindle-shaped, cylindrical, aseptate, typically transparent but occasionally brown (Jiang et al. 2020). The asexual morph of Cryphonectria is a pear-shaped, spherical, or flattened loculate conidiomata. The conidiophores are cylindrical with swollen bases and produce flask-shaped conidiogenous cells and cylindrical conidia that are non-segmented, transparent, and typically elongated (Jiang et al. 2020).

Species Fungorum (2024) listed 26 Cryphonectria epithets. However, with the synonymisation of Cryphonectria decipiens and Cryphonectria naterciae (Rigling & Prospero 2018) and Cryphonectria japonica and Cryphonectria nitschkei (Senanayake et al. 2023), 12 species have been accepted based on morphology and molecular analysis utilising concatenated LSU, ITS, rpb2, β-tubulin (T1/T2), and tef1-α gene regions (Gryzenhout et al. 2009, Braganca et al. 2011, Jiang et al. 2018, 2019, 2020, Senanayake et al. 2023).

Cryphonectria is a hemibiotrophic fungus that includes various important species that cause devastating diseases, notably, C. parasitica is a prominent invasive pathogen that incites necrotic spots (cankers) on the bark of trees (Rigling & Prospero 2018, Stauber et al. 2020). Cryphonectria infect parts of trees above the ground, such as stems, branches, and twigs. The disease shows symptoms of longitudinal splits along the bark (Diller 1965) and light brown mycelial fans (Rigling & Prospero 2018). This ultimately causes wilting in the affected parts of the plant. Cryphonectria infection also induces in production of new shoots below the canker. Less harmful cankers on susceptible host trees are typically linked to mycovirus-induced hypovirulence, resulting in non-lethal, surface-level or callused cankers. Cryphonectria spp. infect various plant hosts including Acer spp. (Aceraceae), Carpinus betulus (Betulaceae), Castanea crenata, C. dentata, C. mollissima, C. pumila, C. sativa (Fagaceae), and Quercus spp. (Fagaceae) (Rigling and Prospero 2018, Dennert et al. 2020). A recent genomic study of Cryphonectria revealed that GH28 genes are responsible for pectin breakdown in C. parasitica. The loss of CAZymes might have boosted the ability of C. parasitica to cause disease in Castanea species (Sprockett et al. 2011, Stauber et al. 2020). Pathogenicity studies demonstrated that C. japonica caused less severe disease than C. parasitica (Dennert et al. 2020) and C. parasitica caused a 52-88 % decline in Castanea sativa and Quercus petraea (Karadžić et al. 2019).

Type species: Cryphonectria parasitica D. Sacc.

Other species: (Species Fungorum – search Cryphonectria)

Figure 1 – Cryphonectria kunmingensis. a Ascostromata on the host surface. d Cross section of ascostromata. c–e Asci. f Ascospores. Scale bars: b = 300 µm, c–e = 20 µm, f = 5 µm. Redrawn from Senanayake et al. (2023).

References

Braganca H, Rigling D, Diogo E, Capelo J et al. 2011 – Cryphonectria naterciae: A new species in the Cryphonectriae – Endothia complex and diagnostic molecular markers based on microsatellite-primed PCR. Fungal biology 115, 852–861.

Dennert F, Rigling D, Meyer JB, Schefer C et al. 2020 – Testing the pathogenic potential of Cryphonectria parasitica and related species on three common European Fagaceae. Frontiers in Forests and Global Change. 3, 52.

Diller JD. 1965 – Chestnut Blight. Forest Pest Leaflet 94. U.S. Department of Agriculture Forest Service, Washington, D.C. 7.

Gryzenhout M, Glen HF, Wingfeld BD, Wingfeld MJ. 2005 – Proposal to conserve the name Cryphonectria (Diaporthales) with a conserved type. Taxon 54, 539–540.

Gryzenhout M, Myburg H, Wingfeld BD, Wingfeld MJ. 2006a – Cryphonectriaceae (Diaporthales), a new family including Cryphonectria, Chrysoporthe, Endothia and allied genera. Mycologia 98, 239–249.

Gryzenhout M, Wingfeld BD, Wingfeld MJ. 2006b – New taxonomic concepts for the important forest pathogen Cryphonectria parasitica and related fungi. FEMS Microbiol Lett 258, 161–172.

Gryzenhout M, Wingfield BD, Wingfield MJ. 2009 – Taxonomy, phylogeny, and ecology of bark-inhabiting and tree-pathogenic fungi in the Cryphonectriaceae. American Phytopathological Society (APS Press).

Jiang N, Fan X, Yang Q, Tian C. 2018 – Two novel species of Cryphonectria from Quercus in China. Phytotaxa 347, 243–250.

Jiang N, Fan XL, Tian CM. 2019 – Identification and pathogenicity of Cryphonectriaceae species associated with chestnut canker in China. Plant Pathology 68(6), 1132–45.

Jiang N, Fan X, Tian C, Crous PW. 2020 – Reevaluating Cryphonectriaceae and allied families in Diaporthales. Mycologia 112, 267–292.

Karadžić D, Radulović Z, Sikora K, Stanivuković Z et al. 2019 – Characterisation and pathogenicity of Cryphonectria parasitica on sweet chestnut and sessile oak trees in Serbia. Plant protection science. 55(3), 191–201.