Name and publication

Phytophthora clandestina P.A. Taylor, Pascoe & F.C. Greenh. (1985)

Taylor PA, Pascoe IE, and Greenhalgh FC. 1985. Phytophthora clandestina sp. nov. in roots of subterranean clover. Mycotaxon 22: 77–85.

Nomenclature

from Taylor et al. (1985)

Mycobank

MB105695

Etymology

from Latin “clandestinus”, meaning hidden or secretive, in recognition of the difficulty encountered in detecting and culturing the fungus (= fungus-like)

Typification

Type: AUSTRALIA, from Kyabram, Victoria, from rooted rots of Trifolium subterraneum subsp. yanninium cv. Yarloop VPRI 12234 preserved in the herbarium of the Plant Research Institute, Burnley, Victoria as microscope slides, dried culture, and infected roots

Ex-type: CBS 347.86

Isotype: specimens are deposited as IMI 2789333 and DAR 49489. P. A. Taylor

Note: IMI 2789333 not available at IMI collection (G. Abad 12.18.17)

Ex-type in other collections

(ET) CBS 347.86, ATCC 58713 (MCI), CABI IMI278933 (PA), WPC P3943 P3652, S&T BL 15 (Abad), 32G1 (Hong), P01 P. A. Taylor, p200 (Gallegly)

Molecular identification

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

Phytophthora clandestina isolate CPHST BL 15 (= P3943 WPC) = ITS rDNA MG865477, COI MH136873

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 clandestina CPHST BL 15
• NCBI: Phytophthora clandestina P3943
• NCBI: Phytophthora clandestina CBS 347.86
• EPPO-Q-bank: Phytophthora clandestina CBS 347.86
• BOLDSYSTEMS: Phytophthora clandestina OOMYA131-07 = CBS34786, PHYTO182-10 = P3943 (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
1b

Morphological identification

Colonies and cardinal temperatures

Phytophthora clandestina grows slowly in culture media including V8-A, PDA, MEA, and lima bean agar. The minimum temperature for growth is 5°C, optimum 25°C, and maximum 31°C.

Asexual phase

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
are papillatepapillate:
pertaining to the production of a distinct papilla at the distal end of the sporangium (cf. nonpapillate and semipapillate)
(often two or three papillae), broadly ellipsoidellipsoid:
refers to a solid body that forms an ellipse in the longitudinal plane and a circle in cross section; many fungal spores are ellipsoidal or elliptic
to ovoidovoid:
egg-shaped, with the widest part at the base of the sporangium and the narrow part at the apex
, sometimes subglobose (16–66 x 15–44 µm), caducouscaducous:
pertaining to sporangia that become dislodged readily (i.e. deciduous) and separate from the sporangiophore (cf. persistent)
with short 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)
(1–6 µm in length), and do not readily separate from sporangiophores at first but become deciduous after zoosporeszoospores:
motile spore that forms within the sporangium and exits through the exit pore and is capable of swimming for several hours; it has both a tinsel flagellum and a whip-like flagellum
have been emitted. A conspicuous dome-shaped or broadly conical basal plugbasal plug:
a plug protruding into a sporangium from the basal cross wall, separating it from the sporangiophore
protrudes into the sporangiumsporangium:
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
. 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
are formed on simple sympodial sporangiophores. Hyphal swellings subspherical to deltoid produced on V-8 juice agar. 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.

Sexual phase

Homothallic. OogoniaOogonia:
the female gametangium in which the oospore forms after fertilization by the antheridium
with smooth wall and usually terminal, rarely intercalaryintercalary:
positioned within a hypha (cf. terminal)
(21–36 µm). Antheridia predominantly paragynousparagynous:
pertaining to the sexual stage in which the antheridium is attached to the side of the oogonium (cf. amphigynous)
(70–90%), but in lima bean agar they are more frequently amphigynousamphigynous:
pertaining to the sexual stage in which the antheridium completely surrounds the stalk of the oogonium (cf. paragynous)
(50–60%). AntheridiaAntheridia:
the male gametangium; a multinucleate, swollen hyphal tip affixed firmly to the wall of the female gametangium (the oogonium)
are terminal or subterminal, occasionally intercalaryintercalary:
positioned within a hypha (cf. terminal)
, and variable in shape (9–45 µm long to 4–17 µm wide), usually delimited by thick basal septum. Amphiginous antheridiaantheridia:
the male gametangium; a multinucleate, swollen hyphal tip affixed firmly to the wall of the female gametangium (the oogonium)
often eccentric about the oogonial stalk. OosporesOospores:
zygote or thick-walled spore that forms within the oogonium after fertilization by the antheridium; may be long-lived
are markedly 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)
(18–31 µm diam) with a wall thickness of 0.3–3.6 µm.

Most typical characters

Phytophthora clandestina is characterized by slow growth at low temperatures, production of typical hyphal swellings, and subterminal or digitate antheridiaantheridia:
the male gametangium; a multinucleate, swollen hyphal tip affixed firmly to the wall of the female gametangium (the oogonium)
. OosporesOospores:
zygote or thick-walled spore that forms within the oogonium after fertilization by the antheridium; may be long-lived
abundantly produced on infected roots and less frequently in culture media.

Specimen(s) evaluated

Phytophthora clandestina CPHST BL 15, duplicate of P3943 (World Phytophthora Collection)

Hosts and distribution

Distribution: Australia
Substrate: roots
Disease note:  major root rot pathogen of subterranean clover (Erwin & Ribeiro 1996)
Hosts: Trifolium subterraneum (subterranean clover, Fabaceae); Medicago spp. are also susceptible (Erwin & Ribeiro 1996)

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

Additional info:
The pathogen infects subterranean clover (Trifolium subterraneum) and is weakly pathogenic on several alfalfa species, including Medicago truncatula, Medicago rugosa, and Medicago scutellata.

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

 

• SMML USDA-ARS: Phytophthora clandestina
• EPPO Global Database: Phytophthora clandestina
• Forest Phytophthoras of the world: Phytophthora clandestina
• CABI Digital Library: Phytophthora clandestina
• Encyclopedia of Life (EOL): Phytophthora clandestina
• Index Fungorum (IF): Phytophthora clandestina

 

• Google All Phytophthora clandestina
• Google Images Phytophthora clandestina
• Google Scholar Phytophthora clandestina

Fact sheet author

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