Abstract
The Nearctic leafhopper Scaphoideus titanus is the primary vector of Flavescence Dorée, a severe grapevine disease in Europe. This insect can complete its life cycle on both cultivated Vitis vinifera and American Vitis species, including rootstock-derived plants that have gone wild. While the movement of S. titanus between wild and cultivated vines is well documented, its biological implications remain unclear, particularly regarding the role of the insect-associated microbiome. In this study, we investigated how rearing S. titanus nymphs on different host plants, including American Vitis and several V. vinifera cultivars, affects its bacterial community. 16S rRNA metabarcoding revealed that the bacterial microbiome was dominated by two obligate symbionts, namely 'Candidatus Karelsulcia' and 'Candidatus Cardinium', with moderate but significant differences in microbial diversity among host plants and developmental stages. When these dominant symbionts were excluded, variability in the remaining bacterial community increased, indicating a modulation of minor taxa according to the plant offered. These findings suggest that host plant species influence the microbiome structure, potentially affecting the insect performance and the microbial exchange between wild and cultivated vines in the field, contributing to disease dynamics.