Xylella fastidiosa, a fastidious phytobacterium threatening northern temperate Europe : insight into potential pathosystems

Xylella fastidiosa, a plant-pathogenic bacterium colonizing xylem and transmitted by insects, is involved in severe outbreaks worldwide. X. fastidiosa establishes in a wide range of conditions including different host plants and vector species, making it highly unpredictable in not yet colonized areas. A quarantine agent in Europe, it has recently been reported as a pest in several Mediterranean European areas, raising questions about the risk of a potential expansion up North. This work investigates the possibility of X. fastidiosa establishing in northern temperate Europe by examining the potential host range and potential insect vectors in these areas. Three different tools were used to investigate host range: mechanical inoculation, transmission via infected vectors, and sentinel plantation. These trials revealed that the Salicaceae include suitable host species that can be colonized by the bacterium, such as Populus tremula and Salix alba. On the other hand, the mobility of two potential insect species for these regions was investigated: Philaenus spumarius and Aphrophora salicina, through flight-mill and mark-release-recapture experiments. Driven by willow distribution, A. salicina proved to be a good flyer. Associated with Salicaceae, this species could transport the bacterium over medium or long distances on plants forming linear corridors in riparian areas or in alignments along crops. These environments could act as reservoirs from which polyphagous vectors as P. spumarius could transmit the bacterium on a local scale to economically important crops. This study highlights one possible scenario and pathosystem for potential long-term establishment and spread of Xylella-related diseases in northern temperate Europe.(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 202