Pythium

Pythium
Scientific classification
(unranked):	SAR
Superphylum:	Heterokonta
Class:	Oomycota
Order:	Pythiales
Family:	Pythiaceae
Genus:	Pythium Pringsheim, 1858
Species
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Pythium is a genus of parasitic oomycotes. 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 frequently a vector for their transmission.

Pythium-induced root rot 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. 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 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 (nor does fallowing the field, as Pythium spp. are also good saprotrophs, and survive for a long time on decaying plant matter).

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