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Slide of the Euphresco project 2018-A-275 'Use of new diagnostic tools for the detection of Pantoea stewartii subsp. stewartii from plants and seeds', Project funded through the Euphresco network

International audience; In conjunction with the emergence of Xylella fastidiosa (Xf) in Europe, several interceptions of coffee plants contaminated with Xf occurred in France. Different XF subspecies and sequence-types (ST) were identified: fastidiosa (ST75), sandyi (ST72 and ST76) and pauca (ST53 and ST74). Since the discovery of a focus of Polygala myrtifolia (Pm) in natural settings in 2015 in Corsica and the French Riviera, this pathogen has been detected on thirty plant species with a validated method based on real time PCR (Harper et al, 2010) associated with a DNA extraction kit (BioNobile). Characterization of isolates directly on plants, or for strains isolated on modified PWG medium is performed according to multilocus sequence typing (MLST) (http://ubmlst.org/xfastidiosa/). Following EPPO protocol PM 7/24, isolates were mostly allocated to sequence types ST6 and ST7 (subspecies multiplex). Mixed infection by ST6 and ST7 was demonstrated by isolation of both strains from one Pm. Modifications to a proposed amplification protocol revealed infections linked to the subspecies pauca, sandyi, one recombinant and some mixed infections. The EPPO protocol MLST confirmed identification of four Pm contaminated with subsp pauca but not the identification of other contaminants. These contaminations were not observed again in the immediate environment after plant eradication. Subspecies assignation directly from plant material is not always successfully linked to PCR inhibitors depending of host plants. This study confirms the diversity of subspecies of Xf in France, but the subspecies multiplex was found to greatly predominate..

International audience; The xylem-limited bacterium Xylella fastidiosa is the causal agent of diseases on a large host range of plants. It has been observed in Americas since the XIXth century causing notably Pierceís disease of grape (Vitis vinifera) in North America, citrus variegated chlorosis on orange tree (Citrus sinensis) in South America and diseases on fruit trees (Prunus dulcis, P. domestica, P. persica, etc.), ornamentals (Coffea spp., Nerium oleander, Platanus occidentalis, etc.) and forest trees (Quercus spp., Ulmus spp., etc.). X. fastidiosa is a quarantine pest for the European Union and as such is listed on the directive 2000/29/EC and the introduction of many plants into the European Union is regulated. A risk of introduction is still pending due to the high number of non-regulated plant hosts which are imported from contaminated areas and to the presence of asymptomatic contaminated plants.