The Phytomyxea are a

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently ...

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 h ...

s that are cosmopolitan, obligate biotrophic protist parasites of plants, diatoms, oomycetes and brown algae. They are divided into the orders

Plasmodiophorida The plasmodiophores (also known as plasmophorids or plasmodiophorids) are a group of obligate endoparasitic protists belonging to the subphylum Endomyxa in Cercozoa. Taxonomically, they are united under a single family Plasmodiophoridae, order P ...

(

ICZN The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its publisher, the I ...

, or

Plasmodiophoromycota The plasmodiophores (also known as plasmophorids or plasmodiophorids) are a group of obligate endoparasitic protists belonging to the subphylum Endomyxa in Cercozoa. Taxonomically, they are united under a single family Plasmodiophoridae, order P ...

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 Phagomyxids are a group of obligate endoparasitic protists belonging to the subphylum Endomyxa in Cercozoa. Taxonomically, they are united under a single family Phagomyxidae, order Phagomyxida, sister to the plasmodiophores. Ecology Phagomyxids ...

. Plasmodiophorids are best known as pathogens or vectors for viruses of arable crops (e.g.

club root Clubroot is a common disease of cabbages, broccoli, cauliflower, Brussels sprouts, radishes, turnips, stocks, wallflowers and other plants of the family Brassicaceae (Cruciferae). It is caused by '' Plasmodiophora brassicae'', which was once co ...

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 in potatoes, and rhizomania in beets, especially

sugar beets Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...

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

in cabbage and its relatives, and powdery scab 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 ve ...

. This ultimately divides to form new spores, which are released when the host's cells burst. Both resting spores and motile zoospores, which generally have two smooth

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have fro ...

, are produced at different stages. Within the plasmodium, dividing nuclei have a distinctive cross-like appearance.

Classification

Plasmodiophorids were traditionally considered slime moulds, 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 fr ...

, and given names such as the

. However, genetic and ultrastructural studies indicate they belong to a diverse group of protists called the

Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major euk ...

, are closely related to them. * Class Phytomyxea Engler & Prantl 1897 em. Cavalier-Smith 1993 ** Genus ?'' Pongomyxa'' ** Order

Cavalier-Smith 1993 *** Family

Phagomyxidae Phagomyxids are a group of obligate endoparasitic protists belonging to the subphylum Endomyxa in Cercozoa. Taxonomically, they are united under a single family Phagomyxidae, order Phagomyxida, sister to the plasmodiophores. Ecology Phagomyxids ...

Cavalier-Smith 1993 **** Genus '' Phagomyxa'' Karling 1944 ** Order

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 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 the ...

'' 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