Phytophthora boehmeriae

Name and publication

Phytophthora boehmeriae Sawada (1927)

Sawada K. 1927. Descriptive catalogue of the Formosan fungi III. Report of the Department of Agriculture, Government Research Institute of Formosa 27: 1–62.


from Sawada (1927)




named for the association with the host Boehmeria nivea


Type: TAIWAN from leaf of Boehmeria nivea (Chinese silk tree, Ramie), 1929, Sawada, IMI 180614

Ex-type: CBS 291.29

Ex-type in other collections:

IMI 180614 = CBS 291.29 (Japan?? incorrect information), P6950 (WOC/WPC), ATCC 60238, CPHST BL 32G (Abad), 45F9 (Yang)

Note about the ex-type: Although HerbIMI cites that a culture of IMI 180614 is available from CABI, specimen IMI 180614 is not available from CABI (search 11.5.2017). In this collection the only specimen available for P. boehmeriae is IMI 403470 from USA, Schmittener's Ohio S833. Isolate IMI 403470 corresponds to ATCC MYA-3893 = P43 (S833, 22G7) cited in ATCC as "key isolate of the species" in Gallegly and Hong 2008. However sequences of MYA-3893 FJ172256, KT183035 (ITS rDNA) don't align with sequences of the duplicate of the ex-type P6950 FJ801955 (ITS rDNA).

Molecular identification

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

Phytophthora boehmeriae isolate CPHST BL 32G (= P6950 WPC) = ITS rDNA MG783382, COI MH136852

Selected specimens

Phytophthora boehmeriae isolate CPHST BL 79 (= P3963 WPC) = ITS rDNA MG783383, COI MH136853

Sequences for ex-type in other sources

NOTE: P. boehmeriae CBS 100410 is a P. like boehmeriae.

Position in ITS phylogenetic tree

Clade 10b

Morphological identification

Colonies and cardinal temperatures

Colony on V8-A is uniform, on PDA and MEA with light chrysanthemum pattern. Minimum temperature for growth is 5°C, optimum is 25°C, and maximum is 33°C.

Conditions for growth and sporulation

Oospores, chlamydospores, and sporangia form abundantly in an agar medium in 7 to 10 days.

Asexual phase

Sporangia papillate, sometimes bipapillate; caducous with short pedicel up to 3 µm long; globose, ellipsoid, obturbinate, obpyriform, and distorted shapes (50–70 L x 35–45 W µm); originated in unbranched or sympodially branching sporangiophores; laterally displaced attachment of sporangiophore is observed. Hyphal swellings absent. Chlamydospores are produced infrequently (40–50 µm diam).

Sexual phase

Homothallic. Oogonia are smooth-walled and hyaline to yellow, antheridia amphigynous and almost spherical in shape, frequently with digitated projection, often with a residual oil globule; oospores plerotic rarely aplerotic, wall is 2 μm or less in thickness.

Most typical characters

P. boehmeriae can be recognized by the production of abundant oogonia and oospores in single culture, amphigynous antheridia, sporangia broadly ovoid to subspherical and conspicuously papillate, and caducous with short pedicel.

Specimen(s) evaluated

Phytophthora boehmeriae CPHST BL 32G duplicate of ex-type P6950 (World Phytophthora Collection, California, USA)

Additional isolates: CPHST BL 79 (Abad) selected specimen duplicate of P3963 from cotton (Gossypium hirsutum) in China

Hosts and distribution

Distribution*: Japan, China, Australia, India (Karnataka and Tamil Nadu states), Argentina, Brazil, Greece, and Papua New Guinea
Substrate: fruits, leaves, roots, bolls
Disease note: causes foliar blight, brown rot of citrus fruit, root rot of Pinus spp., cotton boll blight, basal rot of Gerald ton wax plant (Chamaelauciun uncinatum Schauer.), and gummosis on black wattle (Acacia mearnsii)
Hosts: Citrus spp. (Rutaceae) and various other plant families; Boehmeria nivea (Urticaceae); Gossypium sp. (Malvaceae) cotton

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

*NOTE: The distribution of Phytophthora boehmeriae is in Asia. The distribution of the species in other areas of the world is incorrectly cited in several online sources (including the above).

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.). 

Phytophthora boehmeriae is listed in the U.S. Regulated Plant Pest Table (last modified Nov. 15, 2017).

Additional references and links

Fact sheet author

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