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October 18, 2007
Source: Freshinfo [edited]
<http://www.freshinfo.com/index.php?s=n&ss=nd&sid=43847> [registration required]

A case of potato brown rot has been confirmed in the Irish Republic for the 1st time, sparking a major alert across the industry. The disease, which has been termed the foot-and-mouth of the potato sector, has been identified on a farm in the south-east of the country. Supplies have been recalled and the movement of all stocks halted as an army of inspectors from the department of agriculture tries to trace the source of the infection.

Brown rot poses no risk to animal or human health but is highly infectious and, if allowed to spread, could have devastating consequences for the BPS 56 million (USD 114.65 million) Irish industry and its 700-plus growers. It could also affect the previously high-grade status enjoyed by Irish seed exports.

The usual source of the disease is infected seed or water. In this case, the disease was initially detected in water samples taken at a potato packing premises as part of the department's routine control programme. It was then traced back to a substantial player in the Irish industry, which also supplies seed. These supplies have been recalled for testing and the movement of all stocks on the farm and at packhouses halted, in a bid to prevent the disease spreading. Extensive sampling is being carried out at the farm by department inspectors, but so far the source of the infection has not been identified.

Growers across the republic have been put on alert by the department, and urged to report any signs or suspicions of the disease. "We are working closely with the industry to ensure the outbreak is brought under control as quickly as possible," said a spokesman.

Brown rot is caused by a bacterium called _Ralstonia solanacearum_. Plants start to wilt shortly after infection, stems become discoloured, and the plants eventually die. Potatoes that are affected have a sticky ooze on the eyes and heel of the tuber.

Detection of the disease and the current alert could scarcely have been more ill-timed. Horticulture minister Trevor Sargent has just announced a grant aid programme to develop "a vibrant potato seed sector," which he said is critical for the future of the industry. Funding of around BPS 1.4 m (USD 2.87 m) is aimed at improving the production and marketing infrastructure through investment.

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Communicated by:
ProMED-mail
<promed@promedmail.org>

[Brown rot of potato caused by _Ralstonia solanacearum_ is widely distributed in warm temperate areas. Symptoms include wilting of plants and brown internal staining of tubers. Symptom expression is favoured by temperatures above 15 deg C (59 deg F). The bacteria may also latently infect tubers without causing symptoms and can survive in seed tubers during storage to cause disease when planted in the next season. The pathogen is spread by mechanical means and insects, contaminated equipment, infected plant material (including seed potatoes), and contaminated water (for example in waterlogged fields or drainage channels). Solanaceous and other weeds and unharvested potato plants may serve as pathogen reservoirs.

Yield losses are mostly caused by tuber rotting and, in many warmer areas of the world, brown rot is one of the main limiting factors in potato production. The effect on food- and seed-potato industries can be substantial, and tomato crops are also susceptible. Within the European Community there have been sporadic findings in many member states. The European Plant Protection Organisation (EPPO) has included the pathogen in its quarantine list.

_R. solanacearum_ invades the roots of diverse plant hosts from the soil and aggressively colonises the xylem vessels causing lethal wilting diseases. It was 1st reported as the cause of wilt diseases at the end of the 19th century and is a widely distributed, economically important plant pathogen. It exists as several races affecting more than 200 plant species including major crops such as banana, peanut, potato, tomato, and other solanaceous vegetables. In Europe, race 3 is present and spreading. Races 1 and 2 occur worldwide in tropical climates, with race 2 causing the devastating Moko disease of banana. There are a number of further races of lower economical significance.

Maps
Ireland:
<http://www.fishing-ireland.de/karte.html> and
<http://healthmap.org/promed?v=53.2,-8.2,5>
Worldwide distribution of _R. solanacearum_ race 3 (September 2006):
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum_race3/PSDMS3_map.htm>

Pictures
Brown rot symptoms on potato:
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum/PSDMSO_images.htm> 
and
<http://www.redepapa.org/murcha.jpg>

Links
Disease information:
<http://www.defra.gov.uk/planth/brownrot.htm>
Description and taxonomy of _R. solanacearum_:
<http://expasy.org/sprot/hamap/RALSO.html> and
<http://www.ebi.ac.uk/2can/genomes/bacteria/Ralstonia_solanacearum.html>
History and description of races:
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum/pm7-21(1)%20PSDMSO%20web.pdf>
EPPO quarantine list:
<http://www.eppo.org/QUARANTINE/listA2.htm>. - Mod.DHA]

[see also in the archive:
Moko, Bugtok, blood diseases, banana: research 20070513.1524
2005
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Bacterial wilt, potato - Egypt 20050519.1378
2004
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Clavibacter and Ralstonia, potato - United Kingdom 20040831.2425
Ralstonia solanacearum, potato - Slovakia: 1st report 20040626.1702
Ralstonia solanacearum, survey - United Kingdom 20040110.0109
2003
----
Clavibacter sp., Ralstonia sp., potato - Germany 20030814.2020
2002
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Clavibacter and Ralstonia spp., potato - Germany 20021016.5561
2001
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Clavibacter & ralstonia species, potato - Estonia 20011124.2882
Ralstonia sp., eradicated - France 20010507.0878
2000
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Ralstonia solanacearum, potatoes - Hungary 20001010.1733
Clavibacter & Ralstonia in water: chemical control 20000521.0804
1999
----
Ralstonia solanacearum, potatoes - Syria? (02) 19991210.2143
Ralstonia potato wilt, prevention - France 19990820.1441
Ralstonia solanacearum, potatoes - Syria? 19990703.1117]
 

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