The Phytomyxea are a
class of
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s that are cosmopolitan, obligate biotrophic protist parasites of plants, diatoms, oomycetes and brown algae. They are divided into the orders
Plasmodiophorida (
ICZN, or
Plasmodiophoromycota,
ICBN
The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...
) and
Phagomyxida.
are best known as pathogens or vectors for viruses of arable crops (e.g.
club root in
Brassicaceae
Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The leav ...
,
powdery scab
Powdery scab is a disease of potato tubers. It is caused by the cercozoan ''Spongospora subterranea'' f. sp. ''subterranea'' and is widespread in potato growing countries. Symptoms of powdery scab include small lesions in the early stages of th ...
in potatoes, and
rhizomania in beets, especially
sugar beets and some spinaches).
Life cycle
They typically develop within plant cells, causing the infected tissue to grow into a gall or scab. Important diseases caused by phytomyxeans include
club root in cabbage and its relatives, and
powdery scab
Powdery scab is a disease of potato tubers. It is caused by the cercozoan ''Spongospora subterranea'' f. sp. ''subterranea'' and is widespread in potato growing countries. Symptoms of powdery scab include small lesions in the early stages of th ...
in potatoes. These are caused by species of ''Plasmodiophora'' and ''Spongospora'', respectively.
[Agrios, George N. (2005). ''Plant Pathology''. 5th ed. Academic Press]
link
The vegetative form is a
multinucleate cell, called a
plasmodium
''Plasmodium'' is a genus of unicellular eukaryotes that are obligate parasites of vertebrates and insects. The life cycles of ''Plasmodium'' species involve development in a blood-feeding insect host which then injects parasites into a ver ...
. This ultimately divides to form new spores, which are released when the host's cells burst. Both resting spores and motile
zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves.
Diversity Flagella types
Zoospores may possess one or ...
s, which generally have two smooth
flagella, are produced at different stages. Within the plasmodium, dividing nuclei have a distinctive cross-like appearance.
Classification
Plasmodiophorids were traditionally considered
slime mould
Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mu ...
s, because of the plasmodial stage and are often wrongly classified as
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
, and given names such as the
Plasmodiophoromycota. However, genetic and ultrastructural studies indicate they belong to a diverse group of protists called the
Cercozoa, are closely related to them.
* Class Phytomyxea
Engler & Prantl 1897 em. Cavalier-Smith 1993
** Genus ?''
Pongomyxa''
** Order
Phagomyxida Cavalier-Smith 1993
*** Family
Phagomyxidae Cavalier-Smith 1993
**** Genus ''
Phagomyxa''
Karling 1944
** Order
Plasmodiophorida Cook 1928 em. Cavalier-Smith 1993
*** Family
Endemosarcidae Olive & Erdos 1971
**** Genus ''
Endemosarca''
Olive & Erdos 1971
*** Family
Plasmodiophoridae Berl 1888 (plasmodial slime moulds)
**** Genus ''
Cystospora''
Elliott 1916 nomen dubium 'Acrocystis''_
Ellis_&_Halsted_ex_Halsted_1890_non_Zanardini_1872.html" ;"title="Acrocystis.html" ;"title="'Acrocystis">'Acrocystis''
Ellis & Halsted ex Halsted 1890 non Zanardini 1872">Acrocystis.html" ;"title="'Acrocystis">'Acrocystis''
Ellis & Halsted ex Halsted 1890 non Zanardini 1872**** Genus ''Maullinia''
Maier et al. 2000
**** Genus ''Phytomyxa''
Schröter 1886
**** Genus ''Ligniera''
Maire & Tison 1911 [''Anisomyxa''
Němec 1913; ''
Rhizomyxa''
Borzí 1884; ''
Sorolpidium''
Němec 1911]
**** Genus ''
Membranosporus''
Ostenfeld & Petersen 1930
**** Genus ''
Octomyxa''
Couch, Leitner & Whiffen 1939
**** Genus ''
Plasmodiophora''
Woronin 1877 'Frankiella''_
Maire_&_Tison_1909_non_Speschnew_1900;_''Frankia.html" ;"title="Frankiella.html" ;"title="'Frankiella">'Frankiella''
Maire & Tison 1909 non Speschnew 1900; ''Frankia">Frankiella.html" ;"title="'Frankiella">'Frankiella''
Maire & Tison 1909 non Speschnew 1900; ''Frankia''
Brunchorst 1886 non; ''Ostenfeldiella''
Ferdinandsen & Winge 1914]
**** Genus ''Polymyxa''
Ledingham 1933
**** Genus ''Sorodiscus''
Lagerheim & Winge 1913 non Allman 1847
**** Genus ''
Sorosphaera''
Schröter 1886
**** Genus ''
Sorosphaerula''
Neuh. & Kirchm. 2011
**** Genus ''
Spongospora''
Brunchorst 1887 'Clathrosorus''_
Ferdinandsen_&_Winge_1920.html" ;"title="Clathrosorus.html" ;"title="'Clathrosorus">'Clathrosorus''
Ferdinandsen & Winge 1920">Clathrosorus.html" ;"title="'Clathrosorus">'Clathrosorus''
Ferdinandsen & Winge 1920**** Genus ''Sporomyxa''
Léger 1908
**** Genus ''Tetramyxa''
Goebel 1884 [''Molliardia''
Maire & Tison 1911]
**** Genus ''Woronina''
Cornu 1872
References
{{Taxonbar, from=Q134349
Endomyxa
Parasitic rhizaria
Parasites of plants
Cercozoa classes