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Date: Thu April 2008
Source: European Plant Protection Organisation (EPPO) Reporting Service
4/2008/072 [edited]
<http://archives.eppo.org/EPPOReporting/2008/Rse-0804.pdf>

_Ralstonia solanacearum_ race 3 biovar 2 found in Mauritius

In Mauritius, 2 outbreaks of bacterial wilt (caused by _Ralstonia solanacearum_ -- EPPO A2 List) were recently observed in seed potato fields on different cultivars, at altitudes of about 90 m (295 ft) (one in October 2005 in the south, and the other in September 2006 in the north). In Mauritius, although _R. solanacearum_ has been regularly found, all isolates belonged to race 1 biovar 3. But in October 2005 and September 2006, _R. solanacearum_ race 3 biovar 2 was identified for the 1st time in potato crops, as well as in weed species (_Solanum americanum_, _Lycopersicon pimpinellifolium_, _Oxalis latifolia_). It is considered that _R. solanacearum_ race 3 biovar 2 has recently been introduced onto the island, most probably with latently infected seed potato tubers.

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[Brown rot, also called bacterial wilt, of potato caused by _Ralstonia solanacearum_ is widely distributed in warm temperate areas. Symptoms include wilting of plants and brown internal staining of tubers, and plants
may die. 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.

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

Maps
Mauritius:
<http://www.apple-holidays.com/images/Mauritius/Mauritius_Map.gif> and
<http://healthmap.org/promed?v=-20.3,57.9,5>
Worldwide distribution of _R. solanacearum_ race 3 (September 2006):
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum_race3/PSDMS3_map.htm> 

Pictures of brown rot symptoms:
<http://www.eppo.org/QUARANTINE/bacteria/Ralstonia_solanacearum/PSDMSO_images.htm> 
and
<http://www.redepapa.org/murcha.jpg>
Links
Brown rot 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 A2 quarantine list:
<http://www.eppo.org/QUARANTINE/listA2.htm>. - Mod.DHA]

[see also in the archive:
Potato diseases - India: (West Bengal) 20080206.0477
2007
---
Brown rot, potato - Ireland: 1st report 20071022.3438
2005
---
Bacterial wilt, potato - Egypt 20050519.1378
2004
---
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
---
Clavibacter and Ralstonia spp., potato - Germany 20021016.5561
2001
---
Phytophthora infestans, potato late blight - Russia 20010620.1177
2000
---
Ralstonia solanacearum, potatoes - Hungary 20001010.1733
1999
---
Ralstonia solanacearum, potatoes - Syria? (02) 19991210.2143
Ralstonia potato wilt, prevention - France 19990820.1441
Ralstonia solanacearum, potatoes - Syria? 19990703.1117
Potato & tomato diseases - Europe 19990524.0863]