Xylella fastidiosa, an emerging plant pathogen in Europe that threatens agriculture

The extension of international trading and global changes affect the distribution of diseases posing new threats to food production and preservation of some plant species in the environment. Thus an in-depth knowledge on pathogens, their biology, diversity, and distribution, and ensuring efficient disease diagnosis and pathogen detection are prerequisites for further surveillance strategies and control. Xylella fastidiosa is plant-pathogenic bacterium once restricted to the Americas that recently emerged in Europe. Following its discovery in Italy in 2013, it has been recorded in France, Germany and Spain. It has also been reported from Asian countries such as Taiwan and Iran. X. fastidiosa associates with a large range of plants as more than 350 plant species are listed as hosts of this bacterial species. While X. fastidiosa is responsible for economically important diseases in some crops, ornamentals, and trees, on most host plants it does not cause any symptoms; these plants serving as unseen inoculum reservoir. The only natural means of dispersion of these bacteria are sap-feeding insects. Moreover, X. fastidiosa is a genetically diverse species with several subspecies and a number of clusters of strains that more or less group strains according to host plants and/or diseases. Finally, X. fastidiosa is prone to recombination and in several cases recombination was associated to host shift in field. These characteristics make X. fastidiosa one of the most dangerous plant-pathogenic bacterium that threatens agriculture. We used typing methods and comparative genomics to decipher the putative routes of invasion and assess dispersal schemes in France. Further projects are ongoing to highlight key elements involved in host specificity to predict host range of strains and develop novel identification tests