Dangerous plant disease findings always require international confirmation

11.9.2015

<p>Several tests as well as international confirmation is required when a dangerous plant disease is found in Finland for the first time. When the bacterial disease found in a sample from a pear orchard was identified in the analyses of Finnish Food Safety Authority Evira as fire blight, for the first time ever in Finland, the sample was also sent to Great Britain for an analysis. The tests carried out by the Food and Environment Research Agency (Fera) confirmed the analytical results of Evira.&nbsp;</p>

Early identification of the disease is important to initiate countermeasures on time.

“The final confirmation of the disease was obtained from Fera about three and a half weeks after Evira first received the sample. This is a reasonably short time, considering the sample was analysed with a total of nine different test methods, and some of the tests were repeated several times. Six different screening and identification tests were conducted by Evira, followed by three confirmation tests at Fera”, explains Mirkka Soukainen, who is a Researcher in Evira's Plant Analytics Unit.

In Finland, fire blight analyses have been carried out for decades

Several parallel and consecutive tests are required for the determination of quarantine bacterial diseases. For the determination of fire blight, Evira follows the instructions issued by the European and Mediterranean Plant Protection Organization (EPPO).

”The diagnostic process included antibody tests, which can detect the presence of the bacteria. Parallel to them, also PCR tests that accurately identify certain regions of the DNA of the bacteria were carried out. The identification can be made in real-time on the basis of a signal produced by the PCR equipment, or by amplifying the DNA by conventional PCR and analysing it after the PCR run.The samples were also cultured in plates and the produced bacterial colonies were analysed based on colour, size and other identifying features”, Soukainen elaborates.

In order to determinethe pathogenicity of the bacterial strain isolated from the sample, a healthy host plant was infected with it. In this case, immature apples were used. When the apples developed the typical symptoms of fire blight, such as browning and droplets of sticky bacterial ooze, the bacteria were isolated onto an agar plate. One more identification process was conducted using both a real-time and a conventional PCR method. The identification was confirmed by determining the base sequence of the DNA amplified in the PCR test and comparing it with the gene database.

Until 2014, Finland was the only EU country with no findings of fire blight. The importation of host plants of fire blight has been considerably restricted based on the protection zone status of Finland. In a protection zone, measures shall be taken to prevent the spreading of the disease and to control any occurrences.

Fire blight is the most destructive plant disease of certain fruit trees and ornamental plants of the rose family, caused by the Erwinia amylovora bacteria.

More information about analytics is provided in the following peer-reviewed scientific article:
Soukainen, M., Santala, J., Tegel, J. 
First Report of Erwinia amylovora, the Causal Agent of Fire Blight, on Pear in Finland.
Plant Disease 2015: Vol. 99, No. 7, p. 1033.

Find out more about the activities of the European and Mediterranean Plant Protection Organization EPPO and the Food Environment Research Agency Fera.

For more information, please contact:
Mirkka Soukainen, Researcher, tel. +358 40 583 4943

 

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