Phytophthora aquimorbida

Name and publication

Phytophthora aquimorbida Hong (2012)

Hong CX, Richardson PA, Hao W, Shimire SR, Kong P, Moorman GW, Lea-Cox JD, and Ross DS. 2012. Phytophthora aquimorbida sp. nov. and Phytophthora taxon ‘aquatilis’ recovered from irrigation reservoirs and a stream in Virginia, USA. Mycologia 104: 1097–1108.

Corresponding author:


from Hong et al. (2012)




“Aqui” refers to the habitat where it was isolated, and “morbida” refers to causing diseases.


Type: UNITED STATES OF AMERICA, Virginia, isolated from agricultural irrigation reservoirs, VPI [as 'VTMH'] 11739 dried culture from isolate 40A6 [Virginia Tech Massey Herbarium, Blacksburg, Virginia, USA]

Ex-type: culture ATCC MYA-4578 (40A6)

Sequences for ex-type in original manuscript: Phytophthora sp. CCH-2009b isolate 40A6: in table ITS rDNA: FJ666127; in text β-TUB GQ294534, CO1 GQ294536 and NADH1 GQ294538

Ex-type in other collections

ATCC MYA-4578 = CCH-2009b (40A6) = P19964 (WPC), CPHST BL 128 (Abad), 40A6 (Yang)

Molecular identification

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

Phytophthora aquimorbida isolate CPHST BL 128 (= P19964 WPC) = ITS rDNA MG783376, COI MH136847

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

Clade 9a

Morphological identification

adapted from Hong et al. (2012)

Colonies and cardinal temperatures

Colony growth at 7 days in V8 agar, potato dextrose agar, malt extract agar slight rosette. The minimum temperature for culture growth is 5°C, with an optimum of 30°C, and a maximum of 40°C.

Conditions for growth and sporulation

Sexual structures and some hyphal swellings are produced in culture media including V8 agar. Sporangia are produced only in sterile soil water extract.

Asexual phase

Sporangia nonpapillate, persistent, ovoid to ellipsoidal (28–68 μm long and 21–47 μm wide), borne on unbranched sporangiophores, some with nested or extended proliferation. Hyphal swellings catenulate and radiating are observed in some isolates. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia smooth-walled, globose (24–41 μm diam) some with tapered base, produced terminal, intercalary, or lateral; antheridia amphigynous and are mostly seldom present; oospores plerotic (29–36 μm diam).

Most typical characters

Phytophthora aquimorbida can be distinguished by the intercalary and lateral oogonia sometimes with tapered base.

Additional specimen(s) evaluated

Phytophthora aquimorbida CPHST-BL 128 (Abad) = P19964 [World Phytophthora Collection (WPC) California, USA], duplicate of the ex-type ATCC MYA-4578

Hosts and distribution

Distribution: Virginia, USA
Substrate: Phytophthora aquimorbida C.X. Hong was recovered from irrigation runoff reservoirs in Virginia.
Disease note:  Phytophthora aquimorbida is pathogenic on rhododendron plants and caused root discoloration, pale leaves, wilting, tip necrosis, and dieback.
Hosts: rhododendron

Retrieved January 19, 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