Study of the bacterial community affiliated to Hyalesthes obsoletus (Hemiptera: Cixiidae), the insect vector of Bois Noir phytoplasma of grape

Grape yellows caused by phytoplasmas afflict several important wine-producing areas of Europe. A grape yellows with increasing incidence in European vineyards is “bois noir” (BN), caused by ‘Candidatus Phytoplasma solani’. Its vector is the planthopper Hyalesthes obsoletus Signoret (Hemiptera Cixiidae), occasionally feeding on grapevine. An innovative strategy for reducing the diffusion of the disease could be symbiotic control, exploiting the action of symbiotic microorganisms of the insect host. To investigate the occurrence of possible microbial candidates for symbiotic control we performed a molecular characterization of the bacteria associated to H. obsoletus. Length heterogeneity PCR was applied for a preliminary population screening. Taxonomic affiliations of the bacterial species were analyzed by denaturing gradient gel electrophoresis, showing, within the microbial diversity, the intracellular reproductive parasite Wolbachia pipientis and a Bacteroidetes symbiont with 92% nt identity with ‘Candidatus Sulcia muelleri’. PCR essays specific for these bacteria showed they co-localize in several organs of H. obsoletus. Fluorescent in situ hybridization was performed to assess the distribution of these microorganisms within the insect body, showing interesting localization patterns, particularly in insect gonads and salivary glands. These results could be a starting point for a deeper investigation of functions and relationships between microbial species.