''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but '' Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the

fungus gnat Fungus gnats are small, dark, short-lived gnats, of the families Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae, and Mycetophilidae (order Diptera); they comprise six of the seven families placed in the superfamily Sciaroide ...

are frequently a vector for their transmission.

Morphology

;Hyphae: ''Pythium'' species, like others in the family Pythiaceae, are usually characterized by their production of

coenocytic A coenocyte () is a multinucleate cell which can result from multiple nuclear divisions without their accompanying cytokinesis, in contrast to a syncytium, which results from cellular aggregation followed by dissolution of the cell membranes insid ...

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e without septations. ;Oogonia: Generally contain a single oospore. ;Antheridia: Contain an elongated and club-shaped antheridium.

Ecological importance

''Pythium''-induced

root rot Root rot is a condition in which anoxic conditions in the soil or potting media around the roots of a plant cause them to rot. This occurs due to excessive standing water around the roots. It is found in both indoor and outdoor plants, although ...

is a common crop disease. When the organism kills newly emerged or emerging seedlings, it is known as damping off, and is a very common problem in fields and greenhouses. Thus there is tremendous interest in genetic host resistance, but no crop has ever developed adequate

resistance Resistance may refer to: Arts, entertainment, and media Comics * Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm: ** ''Resistance'' (comics), based on the video game of the same title ** ''T ...

to ''Pythium''. This disease complex usually involves other pathogens such as '' Phytophthora'' and '' Rhizoctonia''. Pythium wilt is caused by zoospore infection of older plants, leading to biotrophic infections that become necrotrophic in response to colonization/reinfection pressures or environmental stress, leading to minor or severe wilting caused by impeded root functioning. Many ''Pythium'' species, along with their close relatives '' Phytophthora'', are

plant pathogens Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...

of economic importance in agriculture. ''Pythium'' spp. tend to be very generalistic and unspecific in their large range of hosts, while ''Phytophthora'' spp. are generally more host-specific. For this reason, ''Pythium'' spp. are more devastating in the root rot they cause in crops, because crop rotation alone often does not eradicate the pathogen as ''Pythium'' spp. are also good

saprotrophs Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi (f ...

, and survive for a long time on decaying plant matter. In field crops, damage by ''Pythium'' spp. is often limited to the area affected, as the motile zoospores require ample surface water to travel long distances. Additionally, the capillaries formed by soil particles act as a natural filter and effectively trap many zoospores. However, in hydroponic systems inside

greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...

s, where extensive monocultures of plants are maintained in plant nutrient solution (containing nitrogen, potassium, phosphate, and

micronutrient Micronutrients are nutrient, essential dietary elements required by organisms in varying quantities throughout life to orchestrate a range of physiological functions to maintain health. Micronutrient requirements differ between organisms; for exam ...

s) that is continuously recirculated to the crop, ''Pythium'' spp. cause extensive and devastating root rot and is often difficult to prevent or control. The root rot affects entire operations (tens of thousands of plants, in many instances) within two to four days due to the inherent nature of hydroponic systems where roots are nakedly exposed to the water medium, in which the zoospores can move freely. Various ''Pythium'' populations have been known to have resistance to

mefenoxam Metalaxyl is an acylalanine fungicide with systemic function. Its chemical name is methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate. It can be used to control ''Pythium'' in a number of vegetable crops, and ''Phytophthora'' in peas. Metalaxy ...

since the 1980s and metalaxyl since 1984. Several ''Pythium'' species, including '' P. oligandrum'', '' P. nunn'', '' P. periplocum'', and '' P. acanthicum'', are mycoparasites of plant pathogenic fungi and oomycetes, and have received interest as potential biocontrol agents.

Species

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Pythium acanthicum ''Pythium acanthicum'' is a plant pathogen infecting strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid species of the genus '' Fragaria'', collectively known as the strawberries, w ...

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Pythium acanthophoron ''Pythium'' is a genus of parasitism, parasitic oomycetes. They were formerly classified as fungus, fungi. Most species are plant parasitism, parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet ...

'' *''

Pythium acrogynum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequentl ...

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Pythium adhaerens ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...

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Pythium amasculinum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequentl ...

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Pythium anandrum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium angustatum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequentl ...

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Pythium aphanidermatum ''Pythium aphanidermatum'' is a soil borne plant pathogen. ''Pythium'' is a genus in the class Oomycetes, which are also known as water molds. Oomycetes are not true fungi, as their cell walls are made of cellulose instead of chitin, they are d ...

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Pythium apleroticum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequen ...

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Pythium aquatile ''Pythium'' is a genus of parasitism, parasitic oomycetes. They were formerly classified as fungus, fungi. Most species are plant parasitism, parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet ...

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Pythium aristosporum ''Pythium aristosporum'' is a species of pythium under the class oomycota (often referred to as water molds) that causes root dysfunction in creeping bentgrass. Hosts and symptoms ''Pythium aristosporum'' causes root dysfunction in creeping b ...

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Pythium arrhenomanes ''Pythium arrhenomanes'' is a plant pathogen. References External links Index FungorumUSDA ARS Fungal Database
Water mould plant pathogens and diseases Pythium, arrhenomanes {{plant-disease-stub ...

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Pythium attrantheridium ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium bifurcatum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...

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Pythium boreale ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequentl ...

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Pythium buismaniae ''Pythium buismaniae'' is a plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that ...

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Pythium butleri ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...

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Pythium camurandrum ''Pythium camurandrum'' is a plant pathogen, first isolated in Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Oc ...

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Pythium campanulatum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium canariense ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium capillosum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium carbonicum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium carolinianum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...

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Pythium catenulatum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium chamaehyphon ''Pythium'' is a genus of parasitism, parasitic oomycetes. They were formerly classified as fungus, fungi. Most species are plant parasitism, parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet ...

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Pythium chondricola ''Pythium porphyrae'', is a parasitic species of oomycete in the family Pythiaceae. It is the cause of red rot disease or red wasting disease, also called ' () in Japanese. The specific epithet ''porphyrae'' () stems from the genus of one ...

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Pythium citrinum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium coloratum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are freque ...

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Pythium conidiophorum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...

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Pythium contiguanum ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequentl ...

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Pythium cryptoirregulare ''Pythium'' is a genus of parasitic oomycetes. They were formerly classified as fungi. Most species are plant parasites, but ''Pythium insidiosum'' is an important pathogen of animals, causing pythiosis. The feet of the fungus gnat are frequent ...

'' *''Pythium cucurbitacearum'' *''Pythium cylindrosporum'' *''Pythium cystogenes'' *''Pythium debaryanum'' *''Pythium deliense'' *''Pythium destruens'' *''Pythium diclinum'' *''Pythium dimorphum'' *''Pythium dissimile'' *''Pythium dissotocum'' *''Pythium echinulatum'' *''Pythium emineosum'' *''Pythium erinaceum'' *''Pythium flevoense'' *''Pythium folliculosum'' *''Pythium glomeratum'' *''Pythium graminicola'' *''Pythium grandisporangium'' *''Pythium guiyangense'' *''Pythium helicandrum'' *''Pythium helicoides'' *''Pythium heterothallicum'' *''Pythium hydnosporum'' *''Pythium hypogynum'' *''Pythium indigoferae'' *''Pythium inflatum'' *'' Pythium insidiosum'' *''Pythium intermedium'' *''Pythium irregulare'' *''Pythium iwayamae'' *''Pythium jasmonium'' *''Pythium kunmingense'' *''Pythium litorale'' *''Pythium longandrum'' *''Pythium longisporangium'' *''Pythium lutarium'' *''Pythium macrosporum'' *''Pythium mamillatum'' *''Pythium marinum'' *''Pythium marsipium'' *''Pythium mastophorum'' *''Pythium megacarpum'' *''Pythium middletonii'' *''Pythium minus'' *''Pythium monospermum'' *''Pythium montanum'' *''Pythium multisporum'' *''Pythium myriotylum'' *''Pythium nagaii'' *''Pythium nodosum'' *''Pythium nunn'' *''Pythium oedochilum'' *''Pythium okanoganense'' *''Pythium oligandrum'' *''Pythium oopapillum'' *''Pythium ornacarpum'' *''Pythium orthogonon'' *''Pythium ostracodes'' *''Pythium pachycaule'' *''Pythium pachycaule'' *''Pythium paddicum'' *''Pythium paroecandrum'' *''Pythium parvum'' *''Pythium pectinolyticum'' *''Pythium periilum'' *''Pythium periplocum'' *''Pythium perniciosum'' *''Pythium perplexum'' *''Pythium phragmitis'' *''Pythium pleroticum'' *''Pythium plurisporium'' *''Pythium polare'' *''Pythium polymastum'' *''Pythium porphyrae'' *''Pythium prolatum'' *''Pythium proliferatum'' *''Pythium pulchrum'' *''Pythium pyrilobum'' *''Pythium quercum'' *''Pythium radiosum'' *''Pythium ramificatum'' *''Pythium regulare'' *''Pythium rhizo-oryzae'' *''Pythium rhizosaccharum'' *''Pythium rostratifingens'' *''Pythium rostratum'' *''Pythium salpingophorum'' *''Pythium scleroteichum'' *''Pythium segnitium'' *''Pythium spiculum'' *''Pythium spinosum'' *''Pythium splendens'' *''Pythium sterilum'' *''Pythium stipitatum'' *''Pythium sulcatum'' *''Pythium tardicrescens'' *''Pythium terrestris'' *''Pythium torulosum'' *''Pythium tracheiphilum'' *''Pythium ultimum'' **Pythium ultimum var. ultimum, ''Pythium ultimum'' var. ''ultimum'' *''Pythium uncinulatum'' *''Pythium undulatum'' *''Pythium vanterpoolii'' *''Pythium viniferum'' *''Pythium violae'' *''Pythium volutum'' *''Pythium zingiberis'' *''Pythium zingiberum'' ''Globisporangium sylvaticum'' was formerly placed here as ''Pythium sylvaticum''

Morphology

Ecological importance

Species

See also

References

Further reading