A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Fri 27 Apr 2012
Source: CTV Winnipeg, The Canadian Press report [edited] <http://winnipeg.ctv.ca/servlet/an/local/CTVNews/20120427/
Crop-damaging disease found in Manitoba soils
Clubroot DNA has been identified for the 1st time in soil samples from Manitoba in 2 separate soil tests. Samples taken last year  from
2 unrelated canola fields in the province show low levels of the disease.
Provincial agriculture officials say it's important for farmers to properly sanitize their field equipment to prevent the spread of soilborne disease.
[Byline: Chris Purdy]
[Clubroot of _Brassicaceae_ is caused by the fungus _Plasmodiophora brassicae_. It is a destructive soilborne disease affecting nearly all cultivated members of the family, including oilseed rape (_Brassica napus_; 'canola' refers to a group of specific varieties), cabbages, and turnip, as well as many wild species which may serve as pathogen reservoirs. It is found worldwide and is most damaging in temperate regions and tropical highlands.
The fungus enters root hairs and wounded roots and multiplies rapidly, causing abnormal enlargement of the underground stem, taproot, or secondary roots ("clubs"). Affected roots often decay before the crop has matured. Depending on the timing of infection in the crop cycle, symptoms may include wilting, stunting, and yellowing of plants, or premature ripening resulting in shriveled seeds. Due to the distortion of the root, plants may wilt in dry weather and then recover at night.
Decaying roots release many resting spores which can survive in the soil for a decade or more in the absence of a susceptible host plant.
The disease can be spread with soil (for example on agricultural machinery), farming activities, and infected plant debris. Disease management is difficult due to the longevity of the spores and the inaccessibility of underground plant parts to fungicides. Raising soil pH by addition of lime has been shown to be effective but is hardly practicable on large fields. Use of clean planting material and phytosanitary measures to prevent spread between fields is essential.
The pathogen is composed of numerous pathotypes, which makes breeding crop cultivars with durable resistance difficult.
In Canada, several of the pathotypes are known to occur in Alberta, and the disease was reported to have arrived in Saskatchewan in 2011 (ProMED-mail post 20111007.3012).
<http://www.lib.utexas.edu/maps/americas/canada_pol_1986.gif> and <http://healthmap.org/r/21SB>
Clubroot symptoms on roots of oilseed rape:
Clubroot affected oilseed rape plants:
<http://www.svfltd.ca/Uploads/contBody1_clubroot.jpg>, and <http://www.canolacouncil.org/clubroot/images/figures/Figure_13_lg.jpg>
Clubroot symptoms on cabbage:
Information on clubroot of oilseed rape:
Information on clubroot on crucifer crops:
Disease cycle of _P. brassicae_:
_P. brassicae_ taxonomy:
Canadian Canola Council clubroot information and updates:
<http://www.canolacouncil.org/clubroot/>. - Mod.DHA]
Clubroot, oilseed rape - Canada: (SK) 20111007.3012
Clubroot, oilseed rape - Canada: (AB), spread 20100118.0206
Clubroot, canola - Canada (02): (AB) 20080916.2899 Clubroot, canola - Canada (SK): alert 20080509.1586 Fungal diseases, oilseed rape - UK, Canada 20080407.1272 Brassica diseases - Turkey, Nepal 20080213.0572
Clubroot, canola - Canada (AB) 20070927.3199
Clubroot, canola - Canada (AB) (02) 20051113.3319 Clubroot, canola - Canada (Alberta) 20050512.1301]