Bacterial associates of Hyalesthes obsoletus (Hemiptera: Cixiidae), the insect vector of bois noir disease, with a focus on cultivable bacteria.

The planthopper Hyalesthes obsoletus (Hemiptera: Cixiidae) is an important vector of phytoplasma diseases in grapevine. In the current study, the bacterial community compositions of symbionts of this insect were examined. Two dominant bacterial lineages were identified by mass sequencing: the obligate symbiont Candidatus Sulcia, and a facultative symbiont that is closely related to Pectobacterium sp. and to BEV, a cultivable symbiont of another phytoplasma vector, the leafhopper Euscelidius variegatus. In addition, one bacterium was successfully isolated in this study - a member of the family Xanthomonadaceae that is most closely related to the genus Dyella. This Dyella-like bacterium (DLB) was detected by FISH analysis in H. obsoletus guts but not ovaries, and its prevalence in H. obsoletus increased during the fall, suggesting that it was acquired by the host through feeding. We found that DLB inhibits Spiroplasma melliferum, a cultivable relative of phytoplasma, suggesting that it is a potential candidate for biological control against phytoplasma in grapevines.