Emergence of Xanthomonas citri pv. citri in Martinique. poster 29

Xanthomonas citri pv. citri, the causal agent of Asiatic citrus canker, is a quarantine pathogen for the European and Mediterranean Protection Plant Organization (EPPO A1 list) and for the European Union (Directive 2000/29/EC annex II A1 – pests absent from the EU). Cases of emergence of this bacterium (Western and Eastern Africa, Australia) correspond to geographical expansion of pathologically - preadapted strains through long distance movement of contaminated plant material. Here we report in Martinique the first outbreak of Asiatic canker in the Caribbean region. The first doubtful lesions were collected mid - 2014 at Morne Rouge from a commercial grove and trees in private gardens when doing surveys targeting huanglongbing, canker and/or other quarantine citrus diseases. A further remote case was identified 12 kilometers away at Le Lorrain in May 2015. Xanthomonas - like cultures were identified and confirmed as X. citri pv. citri on the basis of the EPPO diagnostic protocol PM7/44(1). Strains were further assigned to pathotype A based on pathogenicity tests using a detached leaf assay, MultiLocus Sequence Analysis and MultiLocus Variable number of tandem repeats Analysis targeting 31 minisatellites. The latter technique further assigned outbreak strains to genetic lineage 1, the most widely distributed group of strains. Microsatellite - based genotyping highlighted a very close relatedness between strains f rom the two foci in Martinique. Surprisingly, all strains collected to date in Martinique are copper - resistant even when no extensive copper sprays programs have been used, suggesting that copper - resistant strains were introduced. These initial foci were contained by tree removal and burning and the situation is presently under apparent control. (Texte intégral