Phytophthora citrophthora

Name and publication

Phytophthora citrophthora (R.E. Sm. & E.H. Sm.) Leonian (1925)

Leonian LH. 1925. Physiological studies on the genus Phytophthora. American Journal of Botany 12: 444–498. (Phytophthora citrophthora)





Pythiacystis citrophthora R.E. Sm. & E.H. Sm., Botanical Gazette Crawfordsville 42 (3): 215 (1906) [MB#168281]
Phytophthora imperfecta var. citrophthora (R.E. Sm. & E.H. Sm.) Sarej., Annales de l'Institut Phytopathologique Benaki 2: 46 (1936) [MB#348623]


from Leonian (1925)

Type: UNITED STATES OF AMERICA, California, from citrus in Southern California, Fawcett (isolate)

Ex-type: P0479 (WPC) = Fawcett 1309A

NOTE: Remarks by Leonian (1925) P. citrophthora (Pythiacystis citrophthora Sm. & Sm.) obtained from H. S. Fawcett: "Fungus abundant in winter and spring in Southern California lemon orchards and packing houses, causing serious losses." [notes for basionym: Pythiacystis citrophthora R.E. Sm. & E.H. Sm. (1906)]

Ex-type in other collections

P0479 (WPC) = CBS 950.87ATCC 52231, P. Oudemans P.O. 479, CPHST BL 60 (Abad)

Molecular identification

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

Phytophthora citrophthora isolate CPHST BL 60 (= P0479 WPC) = ITS rDNA MG865476, COI MH136872

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

Clade 2a

Morphological identification

Colonies and cardinal temperatures

Colony grown for 7 days on V8-A, PDA, and MEA with chrysanthemum pattern. Minimum growth temperature 6°C, optimum 24–28°C, maximum 33°C.

Asexual phase

Sporangia semipapillate, some with two papillae; persistent; ovoid, limoniform, ellipsoid, globose, and with distorted shapes, (17–48 x 20–110 µm) some with tapered bases, and with intercalary position, borne in simple sympodial or irregularly branched sporangiophores. Chlamydospores globose, subglobose, lateral, terminal, and intercalary (24–37 µm diam). Hyphal swellings absent.

Sexual phase

Sterile-heterothallic. Oospores rarely produced.

Most typical characters

Phytophthora citrophthora is characterized by the shapes of the semipapillate, persistent sporangia and the chlamydospores.

Specimen(s) evaluated

Phytophthora citrophthora, CPHST BL 60, a duplicate of P0479 (World Oomycetes/Phytophthora Collection), which is a duplicate of Fawcett 1309A

Hosts and distribution

Distribution: cosmopolitan
Substrate: roots, stems, bark of trunk, twigs, leaves, fruits, pods
Disease note: serious gummosis of citrus trees; in historical outbreaks nearly all citrus trees were destroyed (Erwin & Ribeiro 1996). Also root rot, stem necrosis, canker, fruit rot, twig blight, seedling blight; see Erwin & Ribeiro for disease symptoms by host.
Hosts: 88 genera in 51 families

Retrieved January 29, 2018 from U.S. National Fungus Collections Nomenclature Database.

Quarantine status

no quarantine for Phytophthora citrophthora as it is very prevalent and widely distributed around the world

Additional references and links

Leonian LH. 1925. Physiological studies on the genus Phytophthora. American Journal of Botany 12 (7): 444-498. (Phytophthora citrophthora)

Smith RE, Smith EH. 1906. A new fungus of economic importance. Botanical Gazette, 42: 215-221. (Pythiacystis citrophthora)

Mchau GRA and Coffey M. 1994. An integrated study of morphological and isozyme patterns found within a worldwide collection of Phytophthora citrophthora and a redescription of the species. Mycol Re. 98: 1291-1299. NOTE: Not a valid redescription as it is based on multiple isolates and not a neotype or epitype (GA 6.30.14).

Fact sheet author

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