Phytophthora obscura

Name and publication

Phytophthora obscura Grünwald & Werres (2012)

Grünwald NJ, Werres S, Goss EM, Taylor CR, and Fieland VJ. 2012. Phytophthora obscura sp. nov., a new species of the novel Phytophthora subclade 8d. Plant Pathol. 61: 610–622.

Corresponding author:


from Grünwald et al. (2012)




obscura, obscure: referring to the cryptic nature and the fact that it has (to date) not often been found in nature


Type: GERMANY, isolated from soil from Aesculus hippocastanum in 1994 by S. Werres (holotypus: BBA 2/ 94-IIB)

Ex-type: CBS 129273

Sequences for ex-type in original manuscript: BBA 2 ⁄ 94-IIB (type): ITS HQ917910, cox HQ917878, L10 HQ917862, β-tub HQ917870, EF1-A HQ917886, Enl HQ917894, HSP90 HQ917902, 28S HQ917854, TigA HQ917916

Ex-type in other collections

CBS 129273 = P19796 (WOC/WPC), 3106 P-09-003 (N. Grünwald), CPHST BL 84 (Abad), 60E9 (Yang)

Molecular identification

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

Phytophthora obscura isolate CPHST BL 84 (= P19796 WPC) = ITS rDNA MG865554, COI MH136946

Sequences for selected specimen

Phytophthora obscura isolate CPHST BL 85 (= NG3317) = ITS rDNA MG865553, COI MH136945

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

Clade 8d

Morphological identification

adapted from Grünwald et al. (2012)

Colonies and cardinal temperatures

Colony after 7 days of growth on potato dextrose agar with slightly stellate pattern, on V8A with no distinctive pattern. Minimum growth temperature 2°C; optimum 20-25°C and maximum 28°C.

Asexual phase

Sporangia semipapillate; persistent; mainly ovoid and also globose or limoniform (24–50 L × 14–32 W μm); born terminally on unbranched or on simple sympodial sporangiophore. Hyphal swellings absent to rare. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia smooth-walled, predominantly globose, sometimes ellipsoid, tapered base (22–40 μm diam.); antheridia paragynous, nearly globose (6–16 × 6–18 μm); oospores mainly spherical and plerotic to nearly aplerotic (18–36 μm diam.).

Most typical characters

Phytophthora obscura is characterized by the presence of mainly globose sporangia produced in unbranched sporangiophores.

Additional specimen(s) evaluated

Phytophthora obscura CPHST BL 84, duplicate of P19796 (World Oomycetes/Phytophthora Collection), which is a duplicate of ex-type CBS 129273

CPHST BL 85 = NG3317

Hosts and distribution

Distribution: North America (USA: OR), Europe (Germany)
Substrate: leaves, soil
Disease note: leaf blight, canker (?)
Host: Aesculus hippocastanum (Sapindaceae), Pieris sp., Kalmia latifolia (Ericaceae)

Retrieved January 31, 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