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Reportan la presencia de Clavibacter michiganensis con una amplia distribución en los distritos muestreados pero ausencia de Ralstonia (Cuarentenada) en papa en Rusia.

BACTERIAL RING ROT, POTATO - RUSSIA: (NORTHERN)

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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: October 2015

Source: European Plant Protection Organisation (EPPO) Reporting

Service 10/2015/183 [edited]

<http://archives.eppo.int/EPPOReporting/2015/Rse-1510.pdf>

In Northern Russia, surveys of potato bacteria, _Ralstonia solanacearum_ and _Clavibacter michiganensis_ subsp. _sepedonicus_ (both EPPO A2 List), were conducted in the Republic of Karelia (from 2011 to 2013) and in the region of Arkangelsk (from 2012 to 2013). In both Karelia and Arkangelsk, _R. solanacearum_ was not detected but _C. michiganensis_ subsp. _sepedonicus_ was confirmed in several districts.

In Karelia, the largest amounts of infected tubers were detected in regions in the southern part. The bacterium was not detected in samples from northern regions. In Arkangelsk, _C. michiganensis_ subsp. _sepedonicus_ was detected in all surveyed districts.

During these surveys, no disease symptoms were observed (that is, all tested potato tubers were latently infected). Considering the importance of latent infections, an information campaign will be launched to inform potato growers about the risks of moving potentially infected potato material.

[_Clavibacter michiganensis_ subsp. _sepedonicus_ causes ring rot disease of potato. Yield losses of up to 50 percent have been reported. Many solanaceous species, including tomato and aubergine (eggplant), are also susceptible. The pathogen has also been found associated with symptomless infections of sugar beet and sugar beet seed.

Symptoms on potato may include wilting and yellowing of leaves, rot of the vascular ring of tubers with emerging bacterial ooze, and extensive tuber rot followed by internal hollowing, cracking, and mummification. Wilting symptoms may occur late in the season and are often masked by the natural senescence of the crop. Symptom expression depends on host cultivar and is favoured by cool climates. Tubers with ring rot are often subjected to secondary invasions by other bacteria and fungi, which can result in total loss of tubers in the field or in storage.

The pathogen is spread with infected seed tubers or other plant material, plant-to-plant contact, soil, and by mechanical means (for example during harvest or grading). The bacteria can survive for several years on dry surfaces and for over a month in water. They can overwinter in unharvested potatoes or crop debris. Ring rot can pass through one or more crop generations without causing symptoms, and (as mentioned above) latently infected tubers are an important means of spreading the disease. Laboratory tests are needed to detect latent infections.

Disease management is expensive and may include cultural practices and plant hygiene measures before and after harvest, but the use of certified clean seed potatoes is vital. Illegal farm-saved seed potatoes are known to pose a serious risk for the spread of ring rot. _Ralstonia solanacearum_ race 3 (biovar 2, adapted to cooler temperatures) or race 1 (prevalent in warmer areas) causes brown rot (also called bacterial wilt) of potato. These pathogens can also affect tomato and other solanaceous plants. Different races and biovars cause lethal wilting diseases on more than 200 known hosts including many important crops.

In Russia, ring rot has been reported to have caused up to 50 percent regional crop losses in the past. Brown rot is considered a quarantine threat and infected consignments from other countries have been intercepted on several occasions (for example, ProMED-mail post http://promedmail.org/post/20140527.2500654).