|Gehesquière, Bjorn - Institute For Agricultural And Fisheries Research (ILVO)|
|Marra, Robert - Connecticut Agricultural Experiment Station|
|Van Poucke, K - Institute For Agricultural And Fisheries Research (ILVO)|
|Rys, F - Institute For Agricultural And Fisheries Research (ILVO)|
|Maes, M - Institute For Agricultural And Fisheries Research (ILVO)|
|Gobin, B - Botanic Garden|
|Höfte, M - Ghent University|
|Heungens, Kurt - Institute For Agricultural And Fisheries Research (ILVO)|
Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2015
Publication Date: 5/21/2015
Citation: Gehesquière, B., Crouch, J., Marra, R., Van Poucke, K., Rys, F., Maes, M., Gobin, B., Höfte, M., Heungens, K. 2015. Characterization and taxonomic re-assessment of the box blight pathogen Calonectria pseudonaviculata, introducing Calonectria henricotiae sp. nov. Plant Pathology. DOI.org/10.1111/ppa.12401.
Interpretive Summary: Fungi are microscopic organisms that cause billions of dollars in damage to agricultural crops each year. Box blight is a disease of boxwood plants caused by a destructive fungus capable of killing boxwood plants. In this research, fungi isolated from diseased boxwood plants from around the world were analyzed using molecular data to determine which fungal pathogens cause this disease. Two different species of fungi were found to cause box blight in Europe, while only a single fungus was found in the U.S., Asia, and New Zealand. One of the two species in Europe is new to science and is currently only known from Belgium, Germany, the Netherlands, Slovenia, and the United Kingdom. This new species is named, described, and illustrated, and two DNA assays were developed that can be used to distinguish the pathogens. This research will be useful for plant pathologists and breeders who are working to develop ways to control this disease. Plant quarantine personnel will use this research and diagnostic tools to monitor these fungi and to keep the second European species from entering the United States.
Technical Abstract: Calonectria pseudonaviculata, the causal agent of the box blight disease of Buxus spp., was first detected in the mid 1990’s in the United Kingdom and New Zealand. Since then, the geographic range of box blight has rapidly expanded to at least 21 countries throughout temperate regions of the world, causing significant losses to nurserymen and gardeners. In this paper, we determined the genetic diversity from a collection of 232 Calonectria isolated from diseased Buxus plants, originating from 15 countries and four continents. Two genetic clades, G1 and G2, were identified within this sample using multilocus phylogenetic analyis. The application of genealogical concordance species recognition criteria using four independent nuclear loci recognized the Calonectria isolates in these two clades as separate phylogenetic species. The Calonectria isolates in the G1 clade were upheld as C. pseudonaviculuta sensu stricto. Based on phylogenetic distinctiveness, we propose a new species, Calonectria henricotiae sp. nov., for the Calonectria isolates comprising the G2 clade. We developed a PCR-RFLP assay and real-time PCR assays to easily and reproducibly differentiate these species. To assess the practical implications of the identification of the two species, we compared their physiology, fungicide susceptibility and pathogenicity. No differences in pathogenicity were observed. However, C. henricotiae isolates exhibited greater thermotolerance and reduced sensitivity to ten fungicide groups. The identification of a second phylogenetic species causing box blight may have a substantial impact on the epidemiology and control of this destructive disease.