The occurrence of thiabendazole-resistant isolates of Helminthosporium solani on potato seed tubers in Russia

Silver scurf is a potato tuber disease caused by Helminthosporium solani, which has become an increasing problem in many regions of Russia. The fungicide thiabendazole is widely used to control silver scab. Its target of action is the beta-tubulin gene. Single nucleotide mutations in this gene lead to a multiple increase in the resistance of the strain to the fungicide. The resistance of 37 Helminthosporium solani strains to the fungicide thiabendazole was tested in vitro. Tested strains were isolated from potato tubers grown in seven regions of Russia. In this study, the presence of thiabendazole-resistant strains was shown in populations of the European part of Russia, but not for the Far Eastern part. In the Far Eastern part, potatoes are grown from seeds of local production and there is practically no exchange with the European part of Russia. In the present study, we obtain sequences of the beta-tubulin gene and tested the resistance of strains affecting potatoes in the Far Eastern part of Russia to thiabendazole to show the absence of resistant strains. © 2020, Deutsche Phytomedizinische Gesellschaft.