Interlaboratory tests for the detection of Clavibacter michiganensis subsp. sepedonicus (potato ring rot) and Ralstonia solanacearum (potato brown rot)
van Vaerenbergh, Johan; Müller, Petra; Elphistone, John G; Vreeburg, Robert AM; Janse, Jaap D
In the European Union (EU) potato production is surveyed for Clavibacter michiganensis subsp. sepedonicus (potato ring rot) and Ralstonia solanacearum (potato brown rot) under Commission Directives 93/85/EEC with its amendment 2006/56/EC and 98/57/EEC with its amendment 2006/63/EC. A regular update of the Directives is required in view of developments in understanding of the biology of these organisms and the diagnostics recommended for their detection and identification. Three inter-laboratory tests (ILT1, ILT2 and ILT3) were performed from 2009 to 2012 as part of a Euphresco Phytosanitary ERA-NET project to assess performance of current official methods for C. michiganensis subsp. sepedonicus and R. solanacearum. A major aim of the ILTs was to generate data on the performance of real-time PCR protocols to support their introduction as primary (core) screening tests for both pathogens. In ILT1, 29 laboratories from 23 countries participated, in ILT2, 23 laboratories from 18 countries and in ILT3 42 laboratories from 24 countries. Relative accuracies for real-time PCR tests averaged 92% for R. solanacearum and 96% for C. michiganensis subsp. sepedonicus) and compared with existing primary (core) screening tests (immunofluorescence, conventional PCR, semi-selective plating and bioassay) in terms of analytical sensitivity, analytical specificity and robustness. It was concluded that all methods tested, including real-time PCR, can be considered as equivalent. Therefore TaqMan® real-time PCR is recommended for inclusion in EU Directives and EPPO Standards as a reliable primary (core) screening method.