Survey of Fusarium species infecting potato and their resistance to fungicides used in Canada

摘要

Potato seed tubers with symptoms of decay were sampled from across Canada in spring 2010 to obtain a collection of Fusarium isolates. Isolates were identified to species level by microscopic examination of morphological features and molecular methods and then tested for sensitivity to thiabendazole and fludioxonil using a fungicide-amended agar assay. The major seed decay pathogens, F. sambucinum, F. avenaceum and F. coeruleum were frequently recovered. Isolates of F. sambucinum and F. coeruleum varied in their sensitivity to fungicides, with resistance to one or both products found in strains obtained from most Canadian provinces. Isolates of F. avenaceum with varying fungicide resistance were also identified, although most isolates of this species were sensitive to both products. Isolates of F. oxysporum recovered in the survey were always resistant to fludioxonil, but sensitive to thiabendazole. In summary, the survey confirms the presence of strains of F. sambucinum and F. coeruleum in Canada resistant to thiabendazole and/or fludioxonil. As well, fungicide resistance in other Fusarium spp. was also identified. Fungicide resistance has limited the effectiveness of the most common fungicides used against Fusarium spp. on potato seed in Canada. A re-evaluation of management practices for control of Fusarium-induced potato seed-piece decay is required.