Phenotypic variation in Nordic populations of Phytophthora infestans in 2003 |
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| Authors: | A Lehtinen A Hannukkala B Andersson A Hermansen V H Le R Nærstad M B Brurberg B J Nielsen J G Hansen J Yuen |
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| Institution: | MTT Agrifood Research Finland, Plant Production Research, FI-31600 Jokioinen, Finland;;Swedish University of Agricultural Sciences, Dept of Forest Mycology and Pathology, PO Box 7026, S-750 07 Uppsala, Sweden;;Bioforsk-Norwegian Institute for Agricultural and Environmental Research, Høgskoleveien 7, 1432, Norway;;University of Aarhus, Institute of integrated Pest Management, Research Centre Flakkebjerg, Forsoegsvej 1, DK-4200 Slagelse;and;University of Aarhus, Institute of Agroecology, Research Centre Foulum, P.O. Box 50, 8830 Tjele, Denmark |
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| Abstract: | A total of 743 single-lesion isolates of Phytophthora infestans were collected in summer 2003 from Denmark, Finland, Norway and Sweden. Most of the isolates were tested for mating type, and subsets were tested for sensitivity to fungicides and virulence (host specific pathogenicity). Approximately 60% of the isolates were A1 mating type in each country. Both mating types were present in 40% of the fields where more than one isolate was tested, indicating strong potential for sexual reproduction. The proportion of metalaxyl-resistant isolates dropped to under 15% from the 60% observed in the early 1990s in Norway and Finland, possibly due to lower selection pressure because of decreased use of metalaxyl. Propamocarb-HCl sensitivity remained unchanged in the Nordic countries compared to the situation in 1997–2000 in Finland. Four isolates collected from Finland and Sweden were able to sporulate in the presence of this fungicide at a concentration of 1000 mg L?1. In Norway and Finland the frequencies of virulence factors and pathotypes remained nearly unchanged since the 1990s, but the mean number of virulence factors per isolate increased from 5·6 to 6·3. In Denmark and Sweden virulence factors 2 and especially 6 were more common than in Norway and Finland. In addition, in the Swedish population the frequencies of pathotypes were quite even while in other countries pathotype 1,3,4,7,10,11 was most prevalent. |
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| Keywords: | mating type metalaxyl resistance pathotype potato late blight propamocarb-HCl resistance virulence |
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