Variation in populations of Phytophthora infestans in Finland and Norway: mating type, metalaxyl resistance and virulence phenotype

摘要: Phytophthora infestans was isolated from potato leaves and tubers collected different parts of Finland in 1990–96 Norway 1993–96. Isolates were assessed for mating type, resistance to metalaxyl virulence phenotype. In 15% 200 isolates tested 25% 642 A2 type. Differences the A1/A2 ratio evident among regions not found northern areas. frequency metalaxyl-resistant isolates, 1834 tested, decreased 59% 1990–95 2% 1996. 491 resistant Among 269 Finnish 105 Norwegian all known genes both countries race 1.3.4.7.10.11 most common (resistance gene R9 included differential set). Oospores observed three locations southern part Norway. The implications ‘new’ populations Nordic are discussed.