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Late blight pathogen diversity in North-Eastern Europe

Riinu Kiiker: Estonian University of Life Sciences

<div>Crop loss and economic costs can be substantial, when conditions for late blight (<em>Phytophthora infestans</em>) development and spread are favourable in the Baltic countries (Estonia, Latvia and Lithuania). For effective late blight management, knowledge of the contemporary pathogen population in the region is valuable. To reveal<em> P. infestans</em> genotypes and genetic diversity in the Baltic countries over a three-year-period, a 12-plex SSR marker assay was applied to a collection of <em>P. infestans</em> isolates from potato. Overall genetic diversity in the pathogen population was highest in Estonia, followed by Latvia and Lithuania. Most of the multilocus genotypes (MLGs) were identified from a single field outbreak and no MLGs were common to three countries. In Lithuania, the most common local clone was found 19 times over two sampling years whereas, in Latvia, another local clone was found 10 times in one year. In those cases, the samples were from a local cluster of outbreaks. Other repeatedly found local clones were mostly sampled in one year of the study from a single field outbreak and represented by 2−6 isolates. However, none of the clonal lineages found in Western Europe was detected from the Baltic countries. This study reveals the high genetic diversity and possible sexual reproduction in <em>P. infestans</em> populations from the Baltic countries. Most of the <em>P. infestans</em> isolates have unique MLGs with unpredictable phenotypic traits, which may complicate disease management.</div>