Phytophthora hedraiandra

Name and publication

Phytophthora hedraiandra de Cock & Man in ’t Veld (2004)

De Cock AWAM, Lévesque A, 2004. New species of Pythium and Phytophthora. Studies in Mycology 50: 481–488.

Corresponding author: Arthur W.A.M. de Cock,


from De Cock and Lévesque (2004)




refers to the mainly sessile and short-stalked antheridia


Type: THE NETHERLANDS, isolated from leaves of Viburnus sp. CBS H-12856, deposited in herb. CBS

Ex-type: CBS 111725

Sequences for ex-type in original manuscript: CBS 111725 = ITS AY707987 , Cox1 AY769115

Ex-type in other collections

CBS 111725 = P19523 (WPC), CPHST BL 4 (Abad), PD 20017520, 62A5 (Yang)

Molecular identification

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

Phytophthora hedraiandra isolate CPHST BL 4 (= P19523 WPC) = ITS rDNA MG865504, COI MH136898

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

Clade 1a

Morphological identification

adapted from De Cock and Lévesque (2004)

Colonies and cardinal temperatures:

Colonies on V8-A with light chrysanthemum pattern, on PDA and MEA with non-distinctive pattern. Minimum temperature for growth 6°C, optimum 22–24°C, and maximum 30°C.

Conditions for growth and sporulation

Sporangia produced on solid media and water cultures, and chlamydospores mostly observed in old CMA cultures.

Asexual phase

Sporangia papillate; caducous with a very short pedicel (2–5 μm); globose to broadly ovoid or oval, ellipsoid, obpyriform (26–47 L x 21–37 W μm); occasionally single, terminal, or laterally sessile and with lateral displaced attachment; grown mostly on simple sympodial sporangiophores. Hyphal swellings absent. Chlamydospores globose and subglobose, positioned terminally or intercalary.

Sexual phase

Homothallic. Oogonia smooth-walled, globose (24–36 μm diam), sometimes with tapered base, stalk often bent or coiled; antheridia mostly paragynous, occasionally amphigynous, diclinous, rarely monoclinous, spherical, irregular, ellipsoid or ovoid, club-shaped (8–20 L x 7–14 W μm), mostly laterally sessile, occasionally terminal, or unilaterally intercalary, attached near the oogonial stalk, one per oogonium, but in some occasions 2 or more antheridia are observed, some antheridia with spine or digitate projections; oospores aplerotic (20–30 μm diam), wall up to 2 μm thick.

Most typical characters

Phytophthora hedraiandra is characterized by the shape and position of the antheridia including the diclinous origin.

Additional specimen(s) evaluated

Phytophthora hedraiandra ex-type CPHST BL 4, duplicate of P19523 (World Phytophthora Collection), which is a duplicate of ex-type CBS 111725

Hosts and distribution

Distribution: Europe (Hungary, Netherlands, UK), North America (USA: MN)
Substrate: leaves
Disease note: leaf spot, dieback, root rot, collar rot
Hosts: multiple hosts, foliage; Viburnum sp. (Adoxaceae), Rhododendron sp. (Ericaceae)

Retrieved January 30, 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