Phytophthora riparia

Name and publication

Phytophthora riparia Reeser, Sutton, and Hansen (2012)

Hansen EM, Reeser PW, and Sutton W. 2012. Phytophthora borealis and Phytophthora riparia, new species in Phytophthora ITS Clade 6. Mycologia 104: 1133–1142.

Corresponding author:


from Hansen et al. (2012)




refers to the streams and adjacent soils of riparian forests where this species is found


Type: UNITED STATES OF AMERICA, from Oak Creek near Corvallis, Oregon; N44.566593, W-123.300984, collected April 2006, OSC 144,116, dried culture from OSU isolate VI 3-100B9F

Ex-type: MYA-4882 and CBS 132024 

Sequences for ex-type in original manuscript: VI 3-100B9F = ITSrDNA HM004225, β-tub JQ626618, Cox1 JQ626632 , Cox 2, 1 JQ626580

Ex-type in other collections

MYA-4882 = CBS 132024 = P19799 (WOC/WPC), CPHST BL 111 (Abad), 60B1 (Yang)

Molecular identification

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

Phytophthora riparia isolate CPHST BL 111 (= P19799 WPC) = ITS rDNA MG865583, COI MH136975

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

Clade 6b

Morphological identification

adapted from Hansen et al. (2012)

Colonies and cardinal temperatures

Colony morphology on PDA, V8, and MEA with chrysanthemum pattern. Minimum growth temperature 5°C, optimum 25–30°C, and maximum 35°C.

Conditions for growth and sporulation

Sporangia produced on plugs of culture media flooded in soil extract.

Asexual phase

Sporangia nonpapillate; persistent; ovoid, obpyriform (45–65 L x 27–35 W µm); showing nested and extended internal proliferation; originated in unbranched sporangiophores. Hyphal swellings absent. Chlamydospores absent.

Sexual phase


Most typical characters

Phytophthora riparia is characterized by the shape of the sporangia, the type of proliferation, and the sterile character of the sexual phase. 

Additional specimen(s) evaluated

Phytophthora riparia ex-type CPHST BL 111, duplicate of P19799 (World Phytophthora Collection)

Hosts and distribution

Distribution: North America (USA: AK, CA, OR)
Substrate: isolated from stream water, riparian soil

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

Additional info:
Disease note: abundant in stream water, but not overly pathogenic. Not associated with disease in riparian ecosystems.
Hosts: n/a

Additional references and links

Fact sheet author

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