Bacterial microbiota associated with insect vectors of grapevine Bois noir disease in relation to phytoplasma infection.

Bois noir is a grapevine disease causing severe yield loss in vineyards worldwide. It is associated with 'Candidatus Phytoplasma solani', a phloem-limited bacterium transmitted by polyphagous insects. Due to its complex epidemiology, it is difficult to organize effective containment measures. This study aimed to describe the bacterial microbiota associated with 'Candidatus Phytoplasma solani' infected and non-infected insect hosts and vectors to investigate if phytoplasma presence can shape the microbiota. Alpha-diversity analysis showed a low microbiota diversity in these insects, in which few genera were highly abundant. Beta-diversity analysis revealed that the xylem- and phloem-feeding behavior influences the microbiota structure. Moreover, it highlighted that phytoplasma infection is associated with a restructuring of microbiota exclusively in Deltocephalinae insect vectors. Obtained data showed that 'Candidatus Phytoplasma solani' may have adverse effects on the endosymbionts Sulcia and Wolbachia, suggesting a possible fitness modification in the insects. The phytoplasma-antagonistic Dyella was not found in any of the examined insect species. The results indicate an interesting perspective regarding the microbial signatures associated with xylem- and phloem-feeding insects, and determinants that could be relevant to establish whether an insect species can be a vector or not, opening up new avenues for developing microbial resource management-based approaches.