Phytophthora quercetorum

Name and publication

Phytophthora quercetorum Y. Balci & S. Balci (2008)

Balci Y, Balci S, Blair JE, Park SY, Kang S, and MacDonald WL. 2008. Phytophthora quercetorum sp. nov., a novel species isolated from eastern and north-central U.S. oak forests. Mycological Research 112: 906–916 (pp. 911).

Corresponding author:


from Balci et al. (2008)




refers to oak forests


Type: UNITED STATES OF AMERICA, isolated from the rhizosphere soil of oak (Quercus rubra), by Y. Balci in Maryland, Townhill, during July 2004; holotype: BPI 878357 (dry culture deposited to the Herbarium BPI of the Systematic Mycology and Microbiology Laboratory in MD, USA)

Ex-type: CBS 121119 and ATCC MYA-4186 (living cultures)

Sequences for ex-type in original manuscript: P15555 (WPC) = 60S Ribosomal protein L10 EU080900, β-tubulin EU080901, elongation factor 1 alpha EU080902, Enolase EU080903, Heat shock protein 90 EU080904, 28S Ribosomal DNA EU080905, TigA gene fusion EU080906

Ex-type in other collections

CBS 121119 & MYA-4186 = P15555 (WPC), CPHST BL 52G (Abad), Y. Balci MD 9/2

Molecular identification

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

Phytophthora quercetorum isolate CPHST BL 52G (= P15555 WPC) = ITS rDNA MG865577, COI MH136969

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

Clade 4

Morphological identification

adapted from Balci et al. (2008)

Colonies and cardinal temperatures

Colony morphology on PDA, MEA with rosette chrysanthemum pattern. Minimum growth temperature 9°C, optimum 18–24°C, and maximum 30°C.

Conditions for growth and sporulation

Sporangia occasionally produced on culture media and abundantly produced on agar plugs immersed in soil extract water. Gametangia abundantly produced in culture media. 

Asexual phase

Sporangia papillate and occasionally bipapillate; persistent; ovoid, elongated, or distorted shapes (25–44 L x 18–33 W µm) originated in unbranched and simple sympodial sporangiophores or intercalary in hyphae. Sporangiophores with basal or intercalary swellings. Hyphal swellings are not observed but hyphae often present coralloid appearance. Chlamydospores rarely observed and are globose and subglobose.

Sexual phase

Homothallic. Oogonia smooth-walled, globose (17–40 µm), frequently with comma-shaped tapered base on oogonial hyphae; antheridia paragynous, cylindrical or club-shaped; oopores aplerotic or slightly aplerotic (14–33 µm).

Most typical characters

Phytophthora quercetorum is characterized by the presence of oogonia frequently with comma-shaped tapered base and the shape and origin of the sporangia.

Additional specimen(s) evaluated

Phytophthora quercetorum ex-type CPHST BL 52G, duplicate of P15555 (World Phytophthora Collection)

Hosts and distribution

Distribution: North America (USA), Europe
Substrate: soil, rhizosphere
Host: Quercus alba (Fagaceae), Acer rubrum (Sapindaceae), Hedera helix (Araliaceae), Quercus robur

Retrieved February 01, 2018 from U.S. National Fungus Collections Nomenclature Database.

Additional references and links

Fact sheet author

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