Phytophthora primulae (to be redescribed 2022)

Name and publication

Phytophthora primulae Toml. (1952)

Tomlinson JA. 1952. Brown core root rot of Primula caused by Phytophthora primulae n. sp. T. Brit. Mycol. Soc. 35: 221–235.





named for the species from which it was first isolated


from Tomlinson (1958)

Type: UNITED KINGDOM (ENGLAND) isolated from roots of Primula polyantha Mill. causing a stele discoloration and root rot; holotype deposited at the Herbarium Plant Pathology Laboratory, Harpenden, Herts, no. 965, type

Ex-type: LOST

Well-authenticated specimen(s) selected by Gloria Abad: 
Selected specimen #1: Phytophthora primulae CPHST BL 148 = P10703 (WPC) New Zealand from Primulax polyantha Hort.
Selected specimen #2: Phytophthora primulae CPHST BL 50 = P10333 (WPC) Germany from Primula acaulis

Selected specimen #1 in other collections

CBS 114346 = LYN 916-A, ICMP 15183, P10703 (WPC), CPHST BL 148 (Abad)

Molecular identification

Voucher sequences for barcoding genes (ITS rDNA and COI) of selected specimens (see Molecular protocols page)

Phytophthora primulae isolate CPHST BL 148 (= P10703 WPC) = ITS rDNA MG865570, COI MH136962

Phytophthora primulae isolate CPHST BL 50 (= P10333 WPC) = ITS rDNA MG865571, COI MH136963

Sequences for selected specimens in other sources
Position in ITS phylogenetic tree

Clade 8b

Morphological identification

Colonies and cardinal temperatures

Colony morphology on PDA, V8A, MEA with non-distinct pattern. Minimum growth temperature 3°C, optimum 15–21°C, and maximum 27°C.

Conditions for growth and sporulation

Hyphal swellings formed in agar or in soil water extract.

Asexual phase

Sporangia nonpapillate; persistent; ellipsoid, obpyriform, ovoid, or with irregular shapes (33–109 L x 13–39 W µm), many times showing typical constrictions, and sometimes with tapered bases; no internal proliferation is observed but external proliferation originating secondary sporangia is occasionally observed; sporangia mostly originated on unbranched sporangiophores which often present basal and intercalary swellings. Hyphal swellings globose, elongate, or irregular; solitary, catenulated or toruloid kind and clustered; many times with radiating hyphae. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia smooth-walled; spherical to subglobose (20–50 µm diam); antheridia predominantly paragynous and sometimes amphigynous, spherical, ovoid, club-shaped or irregular shape, sometimes with wide antheridial hyphae; oospores aplerotic to slightly aplerotic (17–40 µm diam). Many aborted oospores are observed.

Most typical characters

Phytophthora primulae is characterized by the presence of typical sporangia and hyphal swellings.

Specimen(s) evaluated

Phytophthora primulae CPHST BL 148, duplicate of P10703 (World Phytophthora Collection)

Phytophthora primulae CPHST BL 50, duplicate of P10333 (World Phytophthora Collection), same as CBS 620.97

Hosts and distribution

Distribution: Europe (UK, Denmark), New Zealand
Substrate: roots
Disease note: brown core root rot
Host: Primula spp. (Primulaceae)

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

Quarantine status

USA: 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.).

Additional references and links

Fact sheet author

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