Interlaboratory tests for resistance to Synchytrium endobioticum in potato by the Glynne-Lemmerzahl method

Synchytrium endobioticum is a major quarantine pathogen of potato causing potato wart disease. In Europe, the pathotypes 1(D1), 2(G1), 6(O1) and 18(T1) are the most widespread and occur locally in almost all countries. Resistance to this disease in potato cultivars is tested for in the majority of the EU countries by the Glynne‐Lemmerzahl method. This paper describes the results of testing two different protocols of this method in five laboratories of three different countries (Germany, Poland, and the Netherlands). The four pathotypes 1(D1), 2(G1), 6(O1) and 18(T1) were tested mainly on the cultivars described in the EPPO Standard PM 7/28 Synchytrium endobioticum. For pathotype 1(D1) and in most cases also for pathotype 18(T1), the results of the cultivars tested were identical to the rating in the EPPO Standard for both protocols. For pathotypes 2(G1) and 6(O1), the cultivars Désirée, Delcora and Miriam showed different results between laboratories as well as between the two protocols. In conclusion, further research is needed to develop one harmonised methodology for resistance testing of potato cultivars to the pathotypes 2(G1), 6(O1) and 18(T1) and to develop a new differential set of potato cultivars for the identification of pathotypes of S. endobioticum.