Salicaceae, a potential plant network for the spread of Xylella fastidiosa in temperate regions

Casarin, Noemi [UCL] Hasbroucq, Séverine [UCL] Géradin, Amandine [UCL] Pesenti, Lena [UCL] Emond, Amélie [UCL] Grégoire, Jean-Claude [Spatial Epidemiology lab (SpELL), Université libre de Bruxelles, Brussels, Belgium] Bragard, Claude [UCL] et al.[show all]

Xylella fastidiosa represents a definite threat for Mediterranean flora and southern Europe, as shown by the different outbreaks in France, Italy, Portugal, and Spain. The threat for northern temperate areas is considered more limited based on climate-suitability modelling, but should not be underestimated considering X. fastidiosa in America. The risk for these regions depends mostly on the presence of efficient host plants and insect vectors combinations. Considering this and the scarcity of data about the susceptibility of indigenous European potential host plants, several candidate host plants for Belgium have been evaluated. After a pre-screening by mechanical inoculation, we focused on two Salicaceae, Populus tremula and Salix alba. The family Salicaceae is been associated with several potential insect vectors. It is characteristic of the riparian areas, which have been pointed out to be a favorable niche for both X. fastidiosa and insect vectors. Furthermore, Salicaceae species are also distributed in forests, along the roads and the hydrographic network, therefore having the potential to act as stepping stones in the potential establishment and spread of the pathogen. Our study is carried out by monitoring the bacterial spread and multiplication in the plants after mechanical inoculations under controlled biosafety conditions. The GFP-labeled strain KLN59.3 is used to perform confocal microscopy and scanning electron microscopy to understand the distribution of bacteria in xylem vessels, along with real-time quantitative PCR and re-isolation of the bacteria with the aims to fulfill Koch’s postulates. The research aims at providing scenarios to anticipate the occurrence of such a high-risk pathogen as X. fastidiosa in EU temperate regions, so that appropriate risk reduction options can be rapidly deployed in case of detection in these environments.