A ProMED-mail post <http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>
Date: Fri 19 Oct 2018
Source: Spud Smart [edited]
<http://spudsmart.com/disease-alert/>
Discovered in 3 commercial tomato fields in New York state in the summer of 2018, US-25 was found to be a novel strain by Cornell University. Christine Smart, Cornell, [said], "It was determined to be different than any genotype we had ever seen before." The origins of this new strain remain a mystery. Although US-25 has been found only in tomatoes thus far, Cornell researchers have shown it can infect potato plants under laboratory conditions.
Smart says the fact that US-25 hasn't turned up in potatoes yet may suggest it may not be as aggressive as other genotypes like US-23 and US-8, which have afflicted potato crops in recent years. "US-25 is resistant to metalaxyl but fortunately there are other reliable late blight specific fungicides."
Eugenia Banks, Ontario Potato Board, says one significant aspect of
US-25 is that it's an A2 mating type, unlike the current predominant strain of late blight, US-23, which is A1. If US-25 infects a plant that's also infected with US-23, they can mate which can result in new strains. Having US-23 and US-25 together would be bad news for potato growers.
[Byline: Mark Halsall]
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Communicated by: ProMED-mail <promed@promedmail.org>
[Late blight of tomato and potato is caused by the fungus-like organism (oomycete) _Phytophthora infestans_ and can cause 100 per cent crop loss. The pathogen can also affect some other solanaceous crops. In tomato, it causes lesions and rotting of leaves, stems and fruits; in potato, it affects leaves as well as tubers. The disease is favoured by cool, moist conditions. It can spread rapidly within a crop and destroy it within a few days. Under favourable conditions, epidemics in tomatoes may be even more rapid than in potatoes.
The pathogen is spread by plant material (including tomato transplants, potato seed tubers, plant debris and volunteer crop plants), mechanical means (including human and insect activities), wind and water. Disease management requires an integrated approach and may include removal of pathogen reservoirs, crop rotation, preventive fungicide treatments of planting material and fungicide sprays of crops. Clean planting stock and management strategies for fungicide resistance of the pathogen are vital. Development of resistant cultivars is being counteracted by the adaptability of the pathogen.
Late blight is considered an increasing problem worldwide.
Considerable variation in aggressiveness between different pathogen strains has been observed, but more virulent strains are emerging frequently. Where both A1 and A2 mating types of the pathogen are present, reproduction occurs sexually as well as asexually, increasing the chances of strains with additional fungicide resistances and increased yield losses to develop. All blight outside Mexico was A1 until the mid 1970s when A2 types started to emerge elsewhere.
Maps
USA:
<https://geology.com/world/the-united-states-of-america-map.gif> and <http://healthmap.org/promed/p/106>
Individual states via:
<http://ontheworldmap.com/usa/usa-states-map.html>
Pictures
Late blight on tomato:
<http://ipm.illinois.edu/ifvn/volume15/images/tomato_late_blight.jpg>
Late blight on potato:
<http://farm1.static.flickr.com/81/281344513_74bbffe5fe.jpg> and <http://cdn.phys.org/newman/gfx/news/2013/keepingpacew.jpg> (resistant vs. susceptible cultivars) Microscopy of PLB (potato late blight) infected cells:
<http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/brightfield/images/potatoblight.jpg>
Links
Information on late blight:
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Potato_LateBlt.htm>,
<http://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Pages/LateBlight.aspx>
<https://www.cabi.org/isc/datasheet/40970>, and <http://www.scri.ac.uk/research/pp/pestanddisease/blightepidemiologyandpopulationbiology>
PLB disease cycle:
<http://bit.ly/2lnDBQg>
_P. infestans_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=232148>
Late blight information for USA:
<https://usablight.org/>
Global Initiative on Late Blight:
<https://research.cip.cgiar.org/confluence/display/GILBWEB/Home>
- Mod.DHA]
[See Also:
Late blight, potato - Malawi: (DE)
http://promedmail.org/post/20180817.5971029
Late blight, tomato - UK: new strain susp
http://promedmail.org/post/20180611.5850443
Late blight, potato - India: strain Blue 13
http://promedmail.org/post/20180418.5755980
Late blight, potato - Bangladesh: (RP)
http://promedmail.org/post/20180110.5550872
2017
----
Late blight & post harvest rot, potato - Ireland & UK (NI)
http://promedmail.org/post/20171124.5462543
Late blight, potato - UK: strain Dark Green 37
http://promedmail.org/post/20171029.5412307
Late blight, potato - Bhutan: (CK)
http://promedmail.org/post/20170619.5114985
Late blight, potato - Bangladesh (02): (RP)
http://promedmail.org/post/20170209.4825828
Late blight, potato - Bangladesh: (RS)
http://promedmail.org/post/20170115.4767829
2016
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Late blight, potato - Uganda: (South West)
http://promedmail.org/post/20160602.4260691
Late blight & undiagnosed virus, potato - Bangladesh: (RP)
http://promedmail.org/post/20160121.3953451
2015
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Late blight, potato - Spain: strain Blue13 1st rept, new A1/A2 strains
http://promedmail.org/post/20150317.3237610
Late blight, potato - Nepal: (DN)
http://promedmail.org/post/20150128.3127014
2014
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Late blight, potato - Nigeria, UK
http://promedmail.org/post/20140611.2533396
Late blight, potato & tomato - Canada: strains
http://promedmail.org/post/20140428.2434165
Late blight, potato - Bangladesh: (KH)
http://promedmail.org/post/20140320.2345850
2013
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Late blight, tomato - Oman: (BS)
http://promedmail.org/post/20130603.1752356
Late blight, potato: new strains threat
http://promedmail.org/post/20130111.1492024
and additional items on late blight in the archives]