Phytophthora uniformis

Name and publication

Phytophthora alni subsp. uniformis Brasier & Kirk (2004)

Brasier CM, Kirk SA, Delcan J, Cooke DEL, and Jung T. 2004. Phytophthora alni sp. nov. and its variants: designation of emerging heteroploid hybrid pathogens spreading on Alnus trees. Mycol. Res. 108: 1172–1184.

Corresponding author:

Notes: reclassified as Phytophthora uniformis (Brasier & S.A. Kirk) Husson, Ioos & P. Frey (2015) (SMML). Reclassification under nomenclature evaluation.

Husson C, Aguayo J, Revellin C, Frey P, Ioos R, and Marcais B. 2015. Evidence for homoploid speciation in Phytophthora alni supports taxonomic reclassification in this species complex. Fungal Genet. Biol. 77: 12–21.

Phytophthora alni species complex (alder Phytophthora) Invasive Species Compendium 

The alder Phytophthora species complex of oomycetes encompasses the hybrid P. × alni and its two parental species, P. uniformis and P. × multiformis.


from Brasier et al. (2004) 




from uni and formis meaning of a more uniform phenotype


Type: SWEDEN, Gothenberg, isolated from Alnus bark, 1996, C. Olsson CH161 IMI 392315 (dried culture on carrot agar)

Ex-type: Isolate P875 at the Forestry Commission UK in Phytophthora culture collection

Sequences for ex-type in original manuscript: not provided

Ex-type in other collections

P875 = P875 (Brasier - DEFRA), PD 20019549, 2001 9549 (PPS Wageningen), P16206  (WPC), CPHST BL 3 (Abad)

Molecular identification

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

Phytophthora alni subsp uniformis isolate CPHST BL 3 ( = P16206) ITS rDNA MK496514, COI MH136992

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

Clade 7a

Morphological identification

adapted from Brasier et al. (2004)

Colonies and cardinal temperatures

Colonies in V8 agar, potato dextrose agar, and malt extract agar with no distinctive pattern and slow growth. Minimum growth temperature 3°C, maximum 30°C, and optimum 24–27°C.

Conditions for growth and sporulation

Sporangia produced sparsely in pea broth or when plugs from margins of actively growing cultures on V8-A or PDA are partially submerged in unsterile pond water or unsterile soil leachate.

Asexual phase

Sporangia nonpapillate, persistent, ellipsoid, ovoid, obovoid, obpyriform (28–69 µm length,17–42 µm width) showing internal proliferation and borne single in long sporangiophores. Hyphal swellings absent. Chlamydospores absent.

Sexual phase

Homothallic. Oogonia mostly smooth-walled, but some slightly wavy-edged (verrucose). Occasionally, oogonia have large, distorted beak-like protuberances (37.5–55 µm wide). Antheridia amphigynous and consistently two-celled. The antheridial cross-wall is often close to the base of the antheridium and can be overlooked. Oospore plerotic (overall range ca 30–47.5 µm).

Most typical characters

P. alni subsp. uniformis produces oogonia with a smooth surface and some with slightly wavy edge (verrucose).

Additional specimen(s) evaluated

P. alni subsp. uniformis CPHST-BL # 3 (Abad) = P16206 [World Phytophthora Collection (WPC) California, USA] duplicate of the ex-type P875 Brasier

P. alni subsp. uniformis Abad S511 from Alaska

Hosts and distribution

Distribution: France, Spain, Belgium, Slovenia, USA (Alaska and Oregon)
Substrate: stem/roots
Disease note: root and collar rot
Hosts: Alnus spp. (alder, black alder)

Retrieved January 19, 2018 from U.S. National Fungus Collections Nomenclature Database.

Additional references and links

Adams GC, Catal M, Trummer L, Hansen EM, Reeser P, and Worrall JJ. 2008. Phytophthora alni subsp. uniformis found in Alaska beneath thinleaf alders. Online. Plant Health Progress doi:10.1094/PHP-2008-1212-02-BR.

Aguayo J, Adams GC, Halkett F, Catal M, Husson C, Nagy ZA, Hansen EM, Marçais B, and Frey P. 2013. Strong genetic differentiation between North American and European populations of Phytophthora alni subsp. uniformis. Phytopathology 103: 190–199.

Bakonyi J, Nagi ZA, and Ersek T. 2006. PCR-based DNA markers for identifying hybrids within Phytophthora alni. Journal of Phytopathology 154: 168–177.

Ioos, R., Andrieux, A., Marcais, B., & Frey, P. 2006. Genetic characterization of the natural hybrid species Phytophthora alni as inferred from nuclear and mitochondrial DNA analyses. Fungal Genetics and Biology 43:511–529.

Ioos R, Andrieux A, Marcais B, and Frey P. 2007. New hypothesis on the origin of the interspecific hybrid Oomycete Phytophthora alni. Pages 61–62. in: Fourth Meeting of the IUFRO Working Party S07.02.09 EM Goheen and SJ Frankel, eds. USDA-FS PSW-GTR-221, Monterey, CA, August, 26, 2007.

Pintos Varela C, Rial Martínez C, Aguín Casal O, Mansilla Vázquez JP, and Ares Yebra A. 2012. First report of Phytophthora alni subsp. uniformis on black alder in Spain. Plant Disease 96: 589

Sims L, Navarro S, and Hansen EM. 2012. Phytophthora species isolated from Alnus rubra in western Oregon riparian ecosystems. Proceedings of the 6th Meeting of the International Union of Forest Research Organizations (IUFRO) Working Party S07-02-09 September 9–14, 2012, Còrdoba, Spain. Pg. 46

Winton L. 2012. Phytophthora alni subsp. uniformis) in Alaska

Fact sheet author

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