Xylella fastidiosa and its insect vectors

Xylella fastidiosa is a bacterial pathogen transmitted by insect vectors. In the Americas, the primary vectors are Cicadellidae, subfamily Cicadellinae, i.e. glassy-winged and blue-green sharpshooters whereas in Europe the common meadow spittlebug or froghopper Philaenus spumarius has been identified as the primary vector beside two other spittlebugs, Neophilaenus campestris and Philaenus italosignus. P. spumarius is abundant in Europe, wide-ranging geographically and present in a variety of habitats as well as being highly polyphagous. However, it is important to recognise that although Philaenus spumarius is the most important vector identified at this time, any xylem feeding insect could potentially act as a vector.

Although routine surveillance for X. fastidiosa is carried out on plant material it is also possible to detect the bacterium within the foregut of insects. Recent studies have indicated that, in conjunction with plant surveys, testing vectors for Xylella could be an important tool for monitoring for the bacteria within the wider environment. The main activities of this project focussed on:

• Surveys of potential vector species and association with plant hosts within different habitats including agroecosystems such as vineyards and olive groves collecting data on abundance and host plant preferences.
• Evaluation of sampling and trapping methods for vectors surveillance. Sweep netting is the most effective method and is therefore recommended. However yellow sticky-traps or pan-traps as passive trapping methods also proved to be suitable for monitoring for the presence of spittlebugs.

• Development and evaluation of molecular tests to identify vectors alongside well-established DNA barcoding techniques. CO1 sequences are readily available within GenBank and BOLD for several Philaenus and other species. A specific real-time PCR test was developed for the identification of Philaenus spumarius.
• Development and evaluation of molecular methods (PCR, Real-time PCR and LAMP) for the detection of X. fastidiosa in vectors. CTAB is the most suitable extraction method for the obtention of high concentration of X. fastidiosa genomic DNA from insects. Initial results indicate that although real-time PCR is more sensitive than LAMP, the LAMP test provides advantages as a useful tool for screening vectors in the field.
• A CTAB extraction protocol is the most suitable for the obtention of high concentration of Xf-genomic DNA from insects. Comparative analysis was also undertaken between different molecular techniques (PCR, Real-time PCR and LAMP). Initial results indicate that although qPCR is more sensitive than LAMP that the LAMP assay is a useful tool for screening vectors.