PYTHIUM

(Redirected from Pithium)

'''Pythium''' is a genus of parasitic oomycetes

Contents

Morphology

Ecological Importance

References

See also

Morphology

★ Hyphae
'''Pythium''', like others in the family ''Pythiaceae'', are usually characterized by their production of coenocytic hyphae, hyphae without septations.

★ Oogonia
Generally contain a single oospore

★ Antheridia
Contain an elongated and club-shaped antheridium.

Ecological Importance

'''Pythium''' root rot is a common crop disease caused by a genus of organisms call "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).
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 - that is, they infect a large range of hosts (Owen-Going, 2002) - while ''Phytophthora'' spp. are generally more specific.
For this reason, ''Pythium'' spp. are more devastating in the root rot they cause in field 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. does in field crops is limited to the area affected, because the motile zoospores need ample surface water to travel long distances as 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.

References

★ 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.

See also

★ Pythiosis

★ Water mould

★ Oomycetes

★ Phytophthora

★ Hydroponics