Name and publication

Phytophthora ×multiformis (Brasier & S.A. Kirk) Abad, comb. nov. (2022)

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

Notes: reclassified as Phytophthora x multiformis (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

MB488623

Etymology

from multi and formis meaning multiple forms

Typification

Type: THE NETHERLANDS, isolated from Alnus sp. bark, 1994, H. van Kesteren IMI 392316 (a dried culture on carrot agar) (reported as holotypus)

Ex-type: Isolate P770 at the Forestry Commission UK in Phytophthora culture collection

Sequences for ex-type in original manuscript: P770 = ITS: AF139368

NOTES: Original manuscript (Brasier et al. 2004): The ex-type is of the Dutch phenotypic variant. Owing to the wide array of phenotypes exhibited within subsp. multiformis, it should not be considered phenotypically representative of the entire subspecies but only of this variant. The Dutch, UK, and German variant types are collectively representative phenotypic subpopulations within subsp. multiformis.

Selected specimen in other collections

(SE) WPC P16202, S&T BL 2 (Abad), P770 (Brasier - DEFRA)

Molecular identification

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

Phytophthora alni subsp multiformis isolate CPHST BL 2 (= P16202 WPC) = ITS rDNA MG783372, COI MK493472

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 selected specimen in other sources

• NCBI: Phytophthora alni subsp multiformis CPHST BL 2
• NCBI: Phytophthora alni P16202 (Some sequences as P. alni subsp multiformis others as P. alni)
• EPPO-Q-bank: Phytophthora alni subsp. multiformis P770 
• BOLDSYSTEMS: Phytophthora alni PHYTO126-10 = P16202 (Barcoding COI & ITS)

NOTE: Sequences in NCBI HQ261494, GU259115 have 4bp with AF139368 the sequence of the ex-type in the original manuscript. IMPORTANT: Need to see chromatograms (ABI) files in order to correctly identify this species.

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 and slow growth. Minimum growth temperature 3°C; optimum 23–25°C, and maximum 29°C.

Asexual phase

Semipapillate semipapillate:
pertaining to the production of shallow having papilla that are not well developed, shallow and less nipple-like than fully papillate structures
sporangiasporangia:
sac within which zoospores form, especially when water is cooled to about 10°C below ambient temperature; in solid substrates, sporangia usually germinate by germ tubes
, caducouscaducous:
pertaining to sporangia that become dislodged readily (i.e. deciduous) and separate from the sporangiophore (cf. persistent)
and noncaducousnoncaducous:
pertaining to sporangia that are not dislodged or separated (e.g. persistent) from the sporangiophore (cf. caducous)
, sometimes bipapillate, sometimes terminal, mostly on branched sporangiophores, sympodiallysympodially:
at the foot of; referring to a sporangiophore that emerges externally from the base of the previous sporangium
arranged, 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)
, sometimes mouse-shaped, 25.5–33.5 3 40.0–55.0 mm (mean 30.0 3 47.0 mm), L/B ratio 1.57 : 1, pedicelpedicel:
the hyphal base of a sporangium that remains attached after the sporangium separates, or is shed, from the sporangiophore; the pedicel may be short (< 5 µm), medium (5–20 µm), or long (> 20 µm)
length (M) 8.5–30.0 mm (mean 17.7 mm), ChlamydosporesChlamydospores:
an asexual spore with a thickened inner wall&nbsp;that is delimited from the mycelium by a septum; may be terminal or intercalary, and survives for long periods in soil
 absent, hyphal swellings absent.

Sexual phase

Homothallichomothallic:
pertaining to sexual reproduction that can take place within a single thallus (i.e. self-fertile, non-outcrossing) (cf. heterothallic).
, oogoniaoogonia:
the female gametangium in which the oospore forms after fertilization by the antheridium
globoseglobose:
having a rounded form resembling that of a sphere
, range of means from different strains 26.6–27.9 mm (mean 27.2 mm), oospores plerotic, rarely apleroticaplerotic:
pertaining to a mature oospore that does not fill the oogonium; i.e. there is room left between the oospore wall and oogonium wall (cf. plerotic)
, range of means 24.6–25.8 mm (mean 25.2 mm), antheridiaantheridia:
the male gametangium; a multinucleate, swollen hyphal tip affixed firmly to the wall of the female gametangium (the oogonium)
paragynousparagynous:
pertaining to the sexual stage in which the antheridium is attached to the side of the oogonium (cf. amphigynous)
, rarely amphigynousamphigynous:
pertaining to the sexual stage in which the antheridium completely surrounds the stalk of the oogonium (cf. paragynous)
.

Additional specimen(s) evaluated

P. alni subsp. multiformis CPHST-BL # 2 (Abad) = P16202 [World Phytophthora Collection (WPC) California, USA] duplicate of the ex-type 770

Hosts and distribution

Notes: reclassified as Phytophthora x multiformis (Brasier & S.A. Kirk) Husson, Ioos & P. Frey (2015). Brasier et al. (2004) discuss nomenclatural issues associated with hybrids.

Distribution: Europe (Germany, the Netherlands, UK)
Substrate: roots, collar
Disease note: aggressive root and collar rot of riparian, nursery, and shelterbelt alders
Host: Alnus spp. (alder, Betulaceae)

Retrieved April 14, 2018 from U.S. National Fungus Collections Nomenclature Database.

Quarantine status

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

Phytophthora alni is listed on 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 ×mulitformis
• EPPO Global Database: Phytophthora ×mulitformis
• Forest Phytophthoras of the world: Phytophthora ×mulitformis
• Forest Research UK: Phytophthora ×mulitformis
• Encyclopedia of Life (EOL): Phytophthora ×mulitformis
• Index Fungorum (IF): Phytophthora ×mulitformis

 

• Google All Phytophthora ×mulitformis
• Google Images Phytophthora ×mulitformis
• Google Scholar Phytophthora ×mulitformis

Fact sheet author

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