Pythium species associated with cavity spot on carrots in Norway |
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Authors: | A Hermansen M-L Herrero E Gauslaa J Razzaghian R Nærstad & SS Klemsdal |
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Institution: | Bioforsk-Norwegian Institute for Agricultural and Environmental Research, Plant Health and Plant Protection Division, Hoegskoleveien, Norway |
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Abstract: | Carrot roots with cavity spot lesions from eight different counties in Norway were sampled and Pythium species were isolated on selective medium. Pythium spp. were characterised morphologically and by species-specific PCR. Laboratory experiments with inoculations of carrot roots were performed. A total of 130 isolates out of 230 Pythium -like isolates tested with PCR were identified as pathogenic species of Pythium. These were P. intermedium (29%), P. sulcatum (23%), P. sylvaticum (16%), P. violae (15%) and a possible new Pythium species designated P . ' vipa ' (18%). There were some differences between geographical regions and ages of cavities regarding the frequency of the different species isolated. When rating sunken lesions in the laboratory inoculation experiments, P. ' vipa ' was the most aggressive and P. violae the least aggressive species. P. intermedium and P. ' vipa ' caused more discolouration of the infected carrot tissue than the other species. The importance of the different Pythium spp. as agents of cavity spot in Norway is discussed. |
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Keywords: | Cavity spot Daucus carota morphology PCR Pythium intermedium Pythium sylvaticum Pythium sulcatum Pythium violae Pythium'vipa' |
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