Adaptation of the Method for Detecting Bacterial Diseases of Potato

Bacterial diseases can have a huge impact on potato production yields.
The method for detecting these diseases used in Switzerland to date does not allow the growing demand for tests to be met. Agroscope is implementing new solutions.

The phytopathogenic bacteria Clavibacter sepedonicus (Cs) and Ralstonia solanacearum (Rs) cause ring rot and brown rot of the potato – two quarantine diseases likely to have a major impact on crop productivity.
These diseases form part of the quarantine list in Switzerland, which aims to take drastic measures to contain the most threatening pathogens. At present, the country is free of these two diseases.

Since January 2020, the number of samples to be tested has increased substantially due to the strengthening of the Plant Protection Ordinance. The immunofluorescence microscopy-based method used is not sufficiently rapid, and it is no longer suitable for the volume of samples.

An alternative method enabling the initial screening of the quarantine bacteria was introduced by Agroscope in 2021. The analysis is based on a molecular technique (qPCR). This protocol was compared with the performances of the immunofluorescence microscopy detection method. The results show that there is no difference in sensitivity between the two methods, while qPCR allows a larger number of samples to be processed simultaneously.
The introduction of this method will enable Switzerland to respond to the increased needs associated with the intensification of national monitoring.


  • The current immunofluorescence microscopy method is no longer suitable for analysing the very large number of samples potentially affected by a likewise growing variety of regulated organisms.
  • The new qPCR method is equally sensitive and more accurate for the routine screening of possibly latent Cs and Rs infections.
  • qPCR will enable adaptation to the detection of all known or emerging bacterial organisms in order to support the potato production sector.
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