Microsatellite analysis of European Phytophthora ramorum isolates

Kris Van Poucke, Annelies Vercauteren, Martine Maes, Kurt Heungens

    Research output: Chapter in Book/Report/Conference proceedingC3: Conference Abstract

    Abstract

    Phytophthora ramorum is a destructive pathogen that has caused dieback of oaks and tanoaks in North America since the mid-1990s. In Europe, P. ramorum causes a leaf and twig blight on Rhododendron and Viburnum, and recently has also caused an extensive dieback of Japanese larch in the UK and Ireland. Three lineages (EU1, NA1, NA2) have been described within P. ramorum. The European isolates belong to EU1, while in North America all three lineages have been detected.
    To determine the genetic diversity and pathways of spread in the European P. ramorum population, we conducted microsatellite (MS) analyses of over 1400 isolates originating from the majority of European countries where P. ramorum has been detected. Based on seven microsatellite loci, more than 70 genotypes were identified. A single genotype was dominant, followed in frequency and in isolation year by genotypes with specific single, double, and triple mutations. This indicates that the European P. ramorum population is expanding clonally after the introduction of a single genotype. The population structure was similar in most countries, which was indicative of repeated spread of the most common genotypes followed by local diversification. In some cases, isolates with specific genotypes were detected in different countries, which is a direct indication of international spread. The UK population was different, in that a large proportion of the isolates had a unique mutation in one of the markers, which probably occurred soon after the original introduction. The UK population was also unique in that seven P. ramorum isolates, originating from Northern Ireland and western Scotland, displayed a microsatellite profile that did not match any of the three known P. ramorum lineages. These isolates were analysed with additional inter-lineage polymorphic MS markers. In addition, several genomic and mitochondrial loci were sequenced. Both the MS and multi-locus sequence analysis revealed that these seven UK isolates belong to a novel, fourth P. ramorum lineage, designated EU2. Phylogenetic analysis placed the EU2 lineage ancestral to the other lineages. The seven EU2 isolates were obtained from four hosts (Quercus, Rhododendron, Vaccinium, Larix). The first isolate was collected in 2007, which indicates a relatively recent introduction of this lineage.
    Original languageEnglish
    Title of host publicationabstractbook 64th International Symposium on Crop Protection
    Publication date22-May-2012
    Publication statusPublished - 22-May-2012
    Event64th International Symposium on Crop Protection (2012) - Gent, Belgium
    Duration: 22-May-201222-May-2012
    http://www.iscp.ugent.be/

    Keywords

    • B390-crop-protection

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