Phytophthora porri (to be redescribed 2022)

Name and publication

Phytophthora porri Foister (1931)

Foister CE. 1931. The white tip disease of leeks and its causal fungus, Phytophthora porri n. sp. Transactions of the Botanical Society of Edinburgh. 4: 257–281.

Man in 't Veld WA, de Cock AWAM, Ilieva E, and Lévesque CA. 2002. Gene flow analysis of Phytophthora porri reveals a new species: Phytophthora brassicae sp. nov. Eur. J. Plant Pathol. 108: 51–62.





from Foister (1931)

Type: GREAT BRITAIN, parasitic on leaves and stems of Allium porrum Linn., causing water-logged areas, followed by a whitening of the tips of leaves and other affected parts

Ex-type: LOST

Well-authenticated specimen(s) selected by Gloria Abad: 

Phytophthora porri isolate CPHST BL 147 = P9186

Selected specimen in other collections

CBS 116662 = ADC 00.21b Smilde GG, PD 07 03486421, P9186 (WPC), CPHST BL 147 (Abad)

Molecular identification

Voucher sequences for barcoding genes (ITS rDNA and COI) of selected specimens (see Molecular protocols page)

Phytophthora porri isolate CPHST BL 147 (= P9186 WPC) = ITS rDNA MG865569, COI MH136961

Sequences for selected specimen(s) in other sources
Position in ITS phylogenetic tree

Clade 8b

Morphological identification

Colonies and cardinal temperatures

Colony morphology on PDA, V8A, MEA with rosette pattern. Minimum growth temperature 3°C, optimum 15°C, and maximum 18°C.

Conditions for growth and sporulation

Hyphal swellings formed in agar or in soil water extract.

Asexual phase

Sporangia semipapillate; persistent; obpyriform, ovoid, ellipsoid, or with irregular shapes (16–67 L x 13–39 W µm) sometimes with tapered bases; not proliferating; originated on simple sympodial sporangiophores, often with intercalary swellings. Hyphal swellings globose, ellipsoid, single or in chains. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia smooth-walled; spherical to subglobose (17–40 µm diam); antheridia predominantly paragynous and sometimes amphigynous, globose, short cylindrical or irregular shape; oospores predominantly aplerotic (16–34 µm diam). A high proportion of aborted oogonia are observed.

Most typical characters

Phytophthora porri is characterized by the presence of hyphal swellings and the shape of the sporangia.

Specimen(s) evaluated

Phytophthora porri CPHST BL 147, duplicate of P9186 (World Phytophthora Collection)

CPHST BL 75, duplicate of WPC P7519

Hosts and distribution

Distribution: Africa (South Africa), Asia (Japan), Australia, Europe, North America (Canada). The report from WI, USA is actually Phytophthora brassicae. The report from Canada may be a distinct species (Erwin & Ribeiro 1996).
Substrate: leaves, roots, collars, bulbs
Disease note: leaf blight; shanking; white tip disease; leaf dieback; crown, collar, and root rot
Host: principal host: Allium spp. (Amaryllidaceae); also 5 other genera in 5 families. Not on Brassicaceae; this is a distinct species (Phytophthora brassicae).

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

Additional info:
Host: Allium porrum

Quarantine status

USA: This species was listed as a species of concern during the 2009 Phytophthora prioritization project conducted by USDA APHIS PPQ CPHST PERAL (Schwartzburg et al.).

Additional references and links

Fact sheet author

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