Variation in populations of Phytophthora infestans in Finland and Norway: mating type, metalaxyl resistance and virulence phenotype |
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| Authors: | Hermansen Hannukkala Hafskjold Nærstad & Brurberg |
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| Institution: | The Norwegian Crop Research Institute, Plant Protection Centre, Department of Plant Pathology, Fellesbygget, N-1432 ?s, Norway,;Agricultural Research Centre, Plant Production Research, FIN-31600 Jokioinen, Finland,;Agricultural University of Norway, Department of Horticulture and Crop Sciences, PO Box 5022, N-1432 ?s, Norway |
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| Abstract: | Phytophthora infestans was isolated from potato leaves and tubers collected from different parts of Finland in 1990–96 and Norway in 1993–96. Isolates were assessed for mating type, resistance to metalaxyl and virulence phenotype. In Finland 15% of 200 isolates tested and in Norway 25% of 642 tested were A2 mating type. Differences in the A1/A2 ratio were evident among regions and A2 was not found in northern areas. In Finland the frequency of metalaxyl-resistant isolates, among 1834 tested, decreased from 59% in 1990–95 to 2% in 1996. In Norway 59% of 491 isolates tested were resistant to metalaxyl in 1996. Among 269 Finnish and 105 Norwegian isolates, all known virulence genes were found in both countries and race 1.3.4.7.10.11 was the most common (resistance gene R9 was not included in the differential set). Oospores were observed in potato leaves from three locations in the southern part of Norway. The implications of the 'new' populations in the Nordic countries are discussed. |
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| Keywords: | mating type metalaxyl resistance Phytophthora infestans potato late blight virulence phenotype |
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