Genetic diversity and bacterial community of European populations of Philaenus spp. and Neophilaenus spp., insect vectors of Xylella fastidiosa

The bacterium Xylella fastidiosa causing diseases of relevant impact on several plant species worldwide, is mainly transmitted by xylem-feeding insects of the suborder Auchenorrhyncha. Given the fact that X. fastidiosa poses a serious threat for cultivations in Europe, the knowledge of vectors biology is of great importance. The aim of this study was to explore the genetic diversity (COI, cytb, ITS2) and the bacterial infection status (Wolbachia, Arsenophonus, Hamiltonella, Cardinium, Rickettsia) of different populations of spittlebug species that are either known vectors of the disease or potential vectors. To this end, populations of different spittlebug species were collected from Greece (Philaenus spumarius, P. signatus and Neophilaenus campestris), Italy and Germany (P. spumarius, P. italosignus, N. campestris and N. lineatus). Our study indicated different levels of genetic diversity between the insect species. In the Greek populations of P. spumarius, P. signatus and N. campestris, the ITS2 region was the less polymorphic, while the analyzed fragments of the mitochondrial genes displayed higher genetic diversity. Specimens of P. spumarius from Germany and Italy exhibited high genetic variability in the COI gene while N. campestris from Germany in the ITS2 region. N. lineatus and P. italosignus from Germany and Italy, respectively, displayed low genetic variation. Differences were also detected in the bacterial community harbored by the different insect species collected in the abovementioned countries. Most of the Greek populations harbored at least one symbiont. Rickettsia was the predominant one, while Cardinium was totally absent from all populations. On the other hand, German and Italian specimens displayed lower bacterial diversity, since very few specimens were associated with symbionts. There was no evidence for the presence of Cardinium and Hamiltonella in any of the four examined insect species. The results of this study will enhance the understanding of the insect-endosymbionts-pathogenic bacteria associations and provide important knowledge to develop strategies aiming to control the spread and transmission of the bacterium.GR; PPT; d.kapantaidaki@bpi.g