A ProMED-mail post
http://www.promedmail.org
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International Society for Infectious Diseases
http://www.isid.org

Date: Fri 18 Nov 2022
Source: realagriculture [summ. Mod.DHA, edited]
https://www.realagriculture.com/2022/11/canola-school-verticillium-stripe-continues-to-widen-its-path-across-the-prairies/


First found in 2014 in Manitoba, verticillium stripe has become more common in canola. An excess of moisture and high temperatures in some areas led to a perfect breeding ground for the disease. Therefore, 2022 was the heaviest year on record in Western Canada for verticillium stripe. The disease is still most aggressive in Manitoba but has been located in all 3 prairie provinces. It is moving more intensely towards Saskatchewan and Alberta, getting worse going further east.

Since it is still a relatively new disease in Western Canada, yield impacts under the local conditions are still not entirely certain. Research is currently being conducted for Canadian conditions. In Europe it has been present for about 30 years with yield losses reported from 10-50%.

[byline: Kara Oosterhuis]

--
communicated by:
ProMED

[Verticillium wilt (or stripe) of oilseed rape (_Brassica napus_; "canola" refers to a group of specific varieties) is caused by the soil-borne vascular fungus _Verticillium longisporum_ (Vl). This species is pathogenic only on _Brassica_ species and has been reported from many European countries as well as Japan and the USA. Increasing areas of intense rapeseed cultivation have rendered the pathogen a growing threat to oilseed rape production.

Unlike other _Verticillium_ species, Vl does not induce wilting but premature senescence and ripening, which may severely reduce yields by up to 50%. It can survive in dead plant tissue and soil for up to 20 years. The pathogen can be spread with soil, by contaminated equipment, and with infected plant material (including seed). Disease management is difficult due to the long retention of infectivity of soils and because fungicides are generally not very effective against soil-borne pathogens. Use of clean seed and phytosanitary measures to prevent spread between fields are essential. Biocontrol methods are being investigated. Sufficient genetic resistance is not available in oilseed rape, but interspecific hybridisation may provide a resource for developing resistant crop lines.

Vl appears to be a host-adapted pathogen. Associated microbiomes have recently been found to be a crucial factor in suppressing or enhancing disease development (see link below). Other species in the genus specialise in different host families; for example, solanaceous crops are susceptible to _V. dahliae_; _V. albo-atrum_ is associated with a wilt of hops.

The pathogen had already been present in North America on other brassica hosts when it was first discovered on oilseed rape in Canada (ProMED post 20150108.3077863). Local spread from other hosts to oilseed rape or a new incursion with plant material from, for example, Europe may both have been possible origins of the initial infection.

Maps
Canada (with provinces):
http://mapsof.net/uploads/static-maps/Canada_Provinces_and_territories_map.png

Pictures
Verticillium wilt symptoms on oilseed rape:
https://wwwuser.gwdg.de/~instphyt/app/research/images/verticillium/vl-symptome-gross.jpg
https://wwwuser.gwdg.de/~instphyt/app/research/images/verticillium/staengel-ms-gross.jpg and
https://cropscience.bayer.co.uk/media/86194/verticillium-infected-osr-stems.jpg
Fluorescent microscopy of Vl hyphens on rape roots:
http://wwwuser.gwdg.de/~instphyt/app/research/images/verticillium/vl-root-surface-gross.jpg

Links
Information on Vl wilt/stripe of oilseed rape:
http://wwwuser.gwdg.de/~instphyt/app/research/verticillium.html
https://cropscience.bayer.co.uk/threats/diseases/oilseed-rape-diseases/verticillium-wilt-brassicas-osr/ and
https://doi.org/10.1111/mpp.12350 (review)
Effects of microbiomes on Vl and disease development:
https://doi.org/10.3390/plants9070866 and
https://www.mdpi.com/plants/plants-09-00866/article_deploy/html/images/plants-09-00866-ag-550.jpg
Vl disease cycle:
https://projectblue.blob.core.windows.net/media/Default/Imported%20Publication%20Thumbs/AHDB%20Cereals%20&%20Oilseeds/Disease/Verticillium%20wilt%20(verticillium%20stem%20stripe)%20life%20cycle.jpg
Oilseed rape verticillium in Canada:
https://www.realagriculture.com/2020/04/canola-school-what-weve-learned-about-verticillium-stripe/,
https://www.gov.mb.ca/agriculture/crops/plant-diseases/verticillium-wilt-of-canola-detected-in-manitoba.html and
https://www.inspection.gc.ca/plant-health/plant-pests-invasive-species/plant-diseases/verticillium-stripe/notice-to-industry/eng/1458134997626/1458135081349
_V. longisporum_ taxonomy:
http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=443108
Canola Council Canada:
https://www.canolacouncil.org/
- Mod.DHA]

See Also

2020
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Verticillium wilt, oilseed rape - Canada: (SK) 20201217.8026852
2015
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Verticillium wilt, oilseed rape - North America: 1st report, Canada 20150108.3077863
2010
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Verticillium wilt, oilseed rape - UK: spread 20100330.1005
2008
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Verticillium wilt & sclerotinia, oilseed rape - UK 20080718.2180
2007
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Verticillium wilt, oilseed rape - UK (England): 1st report 20071001.3239
and additional items on other verticillium wilts in the archives

Website: http://www.isid.org

Published: November 25, 2022