Abstract
Monitoring of plant pathogens is usually carried out by analyzing symptomatic plant material. However when plants are frequently asymptomatic, which is the case for Xylella fastidiosa (Xf), this approach is problematic because it limits our ability to early detect the bacterium hence to understand and control its spread. To complement plant survey and facilitate large-scale monitoring, we propose to generalize the use of insect vectors as sentinels. We tested this approach in Corsica using Philaenus spumarius, an ubiquitous insect vector, as sentinel. We will present a high throughput method based on a two-step PCR approach followed by Illumina sequencing. Two genes of the MLST of Xf were targeted to identify the three main subspecies of Xf (multiplex, pauca or fastidiosa). This approach enables larger screening than classic (nested) PCR approaches followed by Sanger sequencing. We used this approach to monitor the spatio-temporal prevalence of Xf within vector populations (27 populations of 30 specimens). Our results show that Xf occurs throughout Corsica with a prevalence in insects up to 43% depending on the region and the year of sampling. Moreover, we show that Xf is present in ecosystems assumed uncontaminated on the basis of plant monitoring. No spatial, temporal or vegetation-related pattern of Xf prevalence in insects seem to emerge from our first data. Our results confirm that Xf introduction in Corsica likely predates 2015, it suggests ecological resilience of ecosystems and argues in favor of using insect vectors for Xf survey at large scale in Europe.