Generally contain a single oospore
Contain an elongated and club-shaped antheridium.
Pythium root rot is a common crop disease caused by a genus of organisms called "Pythium". These are commonly called water moulds. Pythium damping off is a very common problem in fields and greenhouses, where the organism kills newly emerged seedlings (Jarvis, 1992). This disease complex usually involves other fungi as Phytophthora and Rhizoctonia.
Many Pythium species, along with their close relatives, Phytophthora species are plant pathogens of economic importance in agriculture. Pythium spp. tend to be very generalistic and unspecific in their host range. They infect a large range of hosts (Owen-Going, 2002), 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 will often not eradicate the pathogen (nor will fallowing the field, as Pythium spp. are also good saprotrophs, and will survive for a long time on decaying plant matter).
However, the damage Pythium spp. do in field crops is limited to the area affectedthis is because the motile zoospores need ample surface water to travel long distances and the capillaries formed by soil particles act as a natural filter. In hydroponic systems inside greenhouses, where extensive monocultures of plants are maintained in plant nutrient solution (containing nitrogen, potassium, phosphate, and micronutrients) that is continuously recirculated to the crop, Pythium spp. cause extensive and devastating root rot (Jarvis, 1992; Owen-Going, 2002, Owen-Going et al., 2003). The root rot affects entire operations (tens of thousands of plants, in many instances) within two to four days (Owen-Going, 2002, Owen-Going et al., 2003).
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.
- Plaats-Niterink AJ van der. 1981. Monograph of the genus Pythium. Studies in Mycology, 21:1–242.
- Levesque,C.A. and de Cock,A.W. (2004) Molecular phylogeny and taxonomy of the genus Pythium. Mycological Research, 108:1363-1383
- Jarvis, W.R. 1992. Managing diseases in greenhouse crops. APS Press, St. Paul, Minn.
- Owen-Going, T.N. 2002. Etiology and epidemiology of Pythium root rot in bell pepper (Capsicum annuum L.) in commercial-scale and small-scale hydroponic systems. M.Sc. thesis, University of Guelph, Guelph, Ontario.
- Owen-Going, T.N.; Sutton, J.C.; Grodzinski, B. 2003. Relationships of Pythium isolates and sweet pepper plants in single-plant hydroponic units. Canadian Journal of Plant Pathology, 25:155-167.