Phytophthora kernoviae

Name and publication

Phytophthora kernoviae Brasier, Beales & Kirk (2005)

Brasier CM, Beales PA, Kirk SA, Denman S, and Rose J. 2005. Phytophthora kernoviae sp. nov., an invasive pathogen causing bleeding stem lesions on forest trees and foliar necrosis of ornamentals in the UK. Mycol. Res. 109: 853–859.

Corresponding author:

previously known informally as Phytophthora taxon C (PtC)


from Brasier et al. (2005)




from ‘Kernow’, the Cornish noun for Cornwall


Type: UNITED KINGDOM, Cornwall, Caerhays, isolate from bark of Fagus sylvatica, Jan. 2004, C. M. Brasier, IMI 393170 – holotypus, dried culture on carrot agar; previously Forestry Commission Phytophthora culture collection isolate P1571

Ex-type: IMI 393170

NOTE: IMI 393170 indicates that a culture is available from CABI Collection, however a culture of IMI 393170 is not available from CABI.

Sequences for ex-type in original manuscript: Phytophthora kernoviae isolate P1571 (FCPCC) = ITS AY940661

Ex-type in other collections

P1571 (FCPCC) = IMI 393170 = P19827 (WOC/WPC), CAE4, CPHST BL 91 (Abad)

Molecular identification

Voucher sequences for barcoding genes (ITS rDNA and COI) of the ex-type (see Molecular protocols page)

Phytophthora kernoviae isolate CPHST BL 91 (= P19827 WPC) = ITS rDNA MG865521, COI MH136915

Sequences for ex-type in other sources
Position in ITS phylogenetic tree

Clade 10b

Genome sequence

Phytophthora kernoviae strain ex-type P19827. Accession genome CPHST-BL-91 reference, BioProject PRJNA554119, USDA-APHIS-PPQ-S&T (2019), Srivastava et al. 2020

Morphological identification

adapted from Brasier et al. (2005)

Colonies and cardinal temperatures

Colony morphology after 7 days of growth on potato dextrose agar, malt extract agar, and V8 agar with light rosette pattern. Minimum temperature for growth is 3°C, optimum 21°C, and maximum 24°C.

Conditions for growth and sporulation

Sporangia and oospores formed in V8 cultures flooded in 10% soil solution.

Asexual phase

Sporangia papillate; caducous with medium to long pedicels (3–28 µm long); ellipsoid, ovoid, obpyriform, limoniform (19–62 L x 12–31 W µm), mouse-shaped, some with irregular shapes and some with tapered bases; most with conspicuous vacuole; originated in simple sympodial or unbranched sporangiophores. Hyphal swellings coralloid/toruloid occasionally produced. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia smooth-walled, often with tapered base (22–30 µm diam); antheridia amphigynous; oospores spherical (18–28 µm diam) plerotic to slightly aplerotic.

Most typical characters

Phytophthora kernoviae is characterized by the presence of sporangia with caducous medium to long pedicel and by the presence of young oospores with thick walls.

Additional specimen(s) evaluated

Phytophthora kernoviae, ex-type CPHST BL 91, duplicate of P19827 (World Phytophthora Collection), which is a duplicate of ex-type IMI 393170

Hosts and distribution

Notes: previously reported as Phytophthora taxon C

Distribution: Europe (UK); New Zealand, South America (Chile)
Substrate: bark, leaves, shoots
Disease note: on beech, associated with bark necrosis and canker and bleeding stem lesions, especially on aerial stems; pathogenicity confirmed by inoculation studies; also associated with shoot dieback, foliar necroses, and wilting of rhododendron
Host: Fagus sylvatica (beech), Quercus robur (oak), (Fagaceae); also Liriodendron tulipifera (Magnoliaceae), Rhododendron ponticum (Ericaceae), Pinus radiata (Pinaceae)

Retrieved January 31, 2018 from U.S. National Fungus Collections Nomenclature Database.

Quarantine status

USA: Phytophthora kernoviae is listed in the National Cooperative Agricultural Pest Survey (CAPS) Priority Pest List for 2017 and 2018.

This species was listed as a species of concern during the 2009 Phytophthora prioritization project conducted by USDA APHIS PPQ CPHST PERAL (Schwartzburg et al.).

EPPO: organisms previously included in the EPPO Alert List, Phytophthora kernoviae

Additional references and links

Bulletin EPPO 2013

Fact sheet author

Z. Gloria Abad, Ph.D., USDA-APHIS-PPQ-S&T Beltsville Laboratory, United States of America