Name and publication

Phytophthora ×alni Brasier & S.A. 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: clive.brasier@forestry.gsi.gov.uk

Note: reclassified as Phytophthora x alni (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.

Nomenclature

from Brasier et al. (2004) 

Mycobank

MB 631644

Etymology

from Alnus meaning alder

Typification

Type: UNITED KINGDOM, Yorkshire, Doncaster, isolated from Alnus bark (alder, Alnus glutinosa), 1994, G. MacAskill. IMI 392314, dried culture on carrot agar (reported as holotypus)

Ex-type: Isolate P772 at the Forestry Commission UK Phytophthora culture collection

Sequences for ex-type in original manuscript: Isolate P772 ITS rDNA AY689133

Ex-type in other collections

(ET) CABI IMI403468 (AVA) (OLD IMI 392314), P772  (Brasier - DEFRA),  S&T BL 1 (Abad), 47A7 (Hong)

Molecular identification

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

Phytophthora alni subsp alni isolate CPHST BL 1 (= P16203 WPC) ITS rDNA MK496513, COI MH136991

Voucher sequences for Molecular Toolbox with seven genes (ITS, β-tub, COI, EF1α, HSP90, L10, and YPT1

(see Molecular protocols page) (In Progress)

Voucher sequences for Metabarcoding High-throughput Sequencing (HTS) Technologies [Molecular Operational Taxonomic Unit (MOTU)]

(see Molecular protocols page) (In Progress)

Sequences with multiple genes for ex-type in other sources

• NCBI: Phytophthora alni subsp. alni CPHST BL1
• NCBI: Phytophthora alni subsp. alni  IMI 392314
• NCBI: Phytophthora alni subsp. alni  P16203 (some sequences as P. alni subsp alni, others as P. alni)
• EPPO-Q-bank: Phytophthora alni subsp. alni  PD 20019550
• BOLDSYSTEMS: Phytophthora alni subsp. alni OOMYA2163.10 IMI392314 (barcoding COI & ITS)

Position in multigenic phylogeny with 7 genes (ITS, β-tub, COI, EF1α, HSP90, L10, and YPT1)

Clade clade:
a taxonomic group of organisms classified together on the basis of homologous features traced to a common ancestor
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. Minimum growth temperature 3°C, optimum 23–25°C, and maximum 29°C.

Conditions for growth and sporulation

Sporangia form on V8 agar flooded with 10% soil extract; oogoniaoogonia:
the female gametangium in which the oospore forms after fertilization by the antheridium
are usually produced on hemp seed agar amended with fatty oils.

Asexual phase

Sporangia nonpapillate; persistentpersistent:
pertaining to sporangia that remain attached to the sporangiophore and do not separate or detach easily (cf. caducous)
; globoseglobose:
having a rounded form resembling that of a sphere
, ovoidovoid:
egg-shaped, with the widest part at the base of the sporangium and the narrow part at the apex
, obpyriformobpyriform:
inversely pear-shaped, i.e. with the widest part at the point of attachment (cf. pyriform)
(22–65 L x 19–46 W µm), showing nested and extended internal proliferationinternal proliferation:
internal proliferation occurs when the sporangiophore continues to grow through an empty sporangium
and borne in long unbranched or simple sympodial sporangiophores. Hyphal swellings absent. ChlamydosporesChlamydospores:
an asexual spore with a thickened inner wall that is delimited from the mycelium by a septum; may be terminal or intercalary, and survives for long periods in soil
absent.

Sexual phase

Homothallic. OogoniaOogonia:
the female gametangium in which the oospore forms after fertilization by the antheridium
globoseglobose:
having a rounded form resembling that of a sphere
(24–62 µm diam) with ornamented walls showing bullate protuberances and tapered bases; antheridiaantheridia:
the male gametangium; a multinucleate, swollen hyphal tip affixed firmly to the wall of the female gametangium (the oogonium)
predominantly amphigynousamphigynous:
pertaining to the sexual stage in which the antheridium completely surrounds the stalk of the oogonium (cf. paragynous)
, most single-celled but some two-celled; oospores plerotic plerotic:
pertaining to an oospore that fills the oogonium (cf. aplerotic)
(18–52 µm diam).

Most typical characters

P. alni subsp. alni is homothallichomothallic:
pertaining to sexual reproduction that can take place within a single thallus (i.e. self-fertile, non-outcrossing) (cf. heterothallic).
and characterized by the presence of oogoniaoogonia:
the female gametangium in which the oospore forms after fertilization by the antheridium
with ornamented walls showing bullate protuberances and tapered bases.

Additional specimen(s) evaluated

P. alni subsp. alni CPHST-BL # 1 (Abad) = P16203 [World Phytophthora Collection (WPC) California, USA] duplicate of the ex-type P772

Hosts and distribution

Distribution: Sweden, Latvia, Germany, Austria, Italy, Hungary, probably present in or spreading to other parts of Europe. In some locations, such as southern Germany, overlaps with other P. alni subspecies and varieties.
Substrate: Alnus spp., stem/roots
Disease note: associated with root and collar rot of riparian, nursery, and shelterbelt Alnus glutinosa and other Alnus species, including A. incana and A. cordata
Hosts: Alnus glutinosa and other Alnus species, including A. incana and A. cordata

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

Quarantine status

USA:  Phytophthora alni is on the National Cooperative Agricultural Pest Survey (CAPS) Priority Pest Lists for 2017, 2018, and 2019.

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

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

EU: none

EPPO: none

Additional references and links

Brasier CM, Cooke DE, and Duncan JM. 1999. Origin of a new Phytophthora pathogen through interspecific hybridization. Proc. Natl. Acad. Sci. 96: 5878–5883.

Metzler B. 2011. Alder rot caused by Phytophthora alni (in German).

Solla A, Pérez-Sierra A, Corcobado T, Haque MM, Diez JJ, and Jung T. 2010. Phytophthora alni on Alnus glutinosa reported for the first time in Spain. Plant Pathology. 59: 798.

• SMML USDA-ARS: Phytophthora ×alni
• EPPO Global Database: Phytophthora ×alni
• Forest Phytophthoras of the world: Phytophthora ×alni
• Forest Phytophthora of the world: Phytophthora ×alni
• CABI Digital Library: Phytophthora ×alni
• Forest Reserach UK: Phytophthora ×alni
• Encyclopedia of Life (EOL): Phytophthora alni
• Index Fungorum (IF): Phytophthora alni subsp. alni 305732

 

• Google All Phytophthora ×alni
• Google Images Phytophthora ×alni
• Google Scholar Phytophthora ×alni

 

Fact sheet author

Z. Gloria Abad, Ph.D., USDA-APHIS-PPQ-S&T Plant Pathogen Confirmatory Diagnostics Laboratory (PPCDL), United States of America.