Phytophthora macrochlamydospora

Name and publication

Phytophthora macrochlamydospora Irwin (1991)

Irwin JAG. 1991. Phytophthora macrochlamydospora, a new species from Australia. Mycologia 83: 517–519.





from Irwin (1991)

Type: AUSTRALIA, from soybean (Glycine max), collected Indooroopilly, Queensland, collected in 13 Feb. 1974, J. A. G. Holotypus BRIP 17047.

Ex-type: Irwin 20502

NOTE: Irwin 20502 deposited WPC P10263.

Ex-type in other collections

Irwin 20502 = P10263 (WPC), DP1 20502 (CRCTPP)], UQ205, CPHST BL 71 (Abad)

Molecular identification

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

Phytophthora macrochlamydospora isolate CPHST BL 71 (= P10263 WPC) = ITS rDNA MG865528, COI MH136923

Sequences for ex-type in other sources
  • NCBI: Phytophthora macrochlamydospora CPHST BL 71
  • NCBI: Phytophthora macrochlamydospora P10263
  • Phytophthora DATABASE: Phytophthora macrochlamydospora PD_01248 = P10263 (WPC)
  • EPPO-Q-bank: Phytophthora macrochlamydospora
  • BOLDSYSTEMS: Phytophthora macrochlamydospora (barcoding COI & ITS)
Position in ITS phylogenetic tree

Clade 10a

Genome sequence

Phytophthora macrochlamydospora strain ex-type BL 71. Accession genome USDA_Pmac_71_1.0, BioProject PRJNA612532, USDA APHIS PPQ S&T 2020

Morphological identification

Colonies and cardinal temperatures

Colony morphology after 7 days of growth on potato dextrose agar and malt extract agar with chrysanthemum pattern, and on V8 agar with light chrysanthemum pattern. Minimum temperature for growth is 6°C, optimum 23–30°C, and maximum 34°C. 

Conditions for growth and sporulation

Hyphal swellings and chlamydospores produced in solid and liquid media.

Asexual phase

Sporangia nonpapillate and semipapillate; persistent; ellipsoid, obpyriform (20–50 L x 18–36 W µm); showing internal proliferation; originated on unbranched sporangiophores up to 500 µm long. Hyphal swellings spherical to ellipsoid, catenulate or solitary. Chlamydospores spherical (28–84 µm diam), terminal or intercalary.

Sexual phase


Most typical characters

Phytophthora machrochlamydospora is characterized by the production of abundant thick-walled chlamydosporescatenulated globose to elongated hyphal swellings, and the sterile condition of the sexual stage of the species.

Specimen(s) evaluated

Phytophthora macrochlamydospora ex-type CPHST BL 71, duplicate of P10263 (World Phytophthora Collection), which is a duplicate of Irwin 20502

Hosts and distribution

Distribution: Australia
Substrate: stems, roots
Disease note: stem and root rot
Host: Glycine max (soybean, Fabaceae)

Retrieved January 31, 2018 from U.S. National Fungus Collections Nomenclature Database.

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