ABSTRACT
Flavescence dorée (FD) is a grapevine disease that afflicts several wine production areas in Europe, from Portugal to Serbia. FD is caused by a bacterium, “
Candidatus
Phytoplasma vitis,” which is spread throughout the vineyards by a leafhopper,
Scaphoideus titanus
(Cicadellidae). After collection of
S. titanus
specimens from FD-contaminated vineyards in three different areas in the Piedmont region of Italy, we performed a survey to characterize the bacterial microflora associated with this insect. Using length heterogeneity PCR with universal primers for bacteria we identified a major peak associated with almost all of the individuals examined (both males and females). Characterization by denaturing gradient gel electrophoresis confirmed the presence of a major band that, after sequencing, showed a 97 to 99% identity with
Bacteroidetes
symbionts of the “
Candidatus
Cardinium hertigii” group. In addition, electron microscopy of tissues of
S. titanus
fed for 3 months on phytoplasma-infected grapevine plants showed bacterial cells with the typical morphology of “
Ca.
Cardinium hertigii.” This endosymbiont, tentatively designated ST1-C, was found in the cytoplasm of previtellogenic and vitellogenic ovarian cells, in the follicle cells, and in the fat body and salivary glands. In addition, cell morphologies resembling those of “
Ca.
Phytoplasma vitis” were detected in the midgut, and specific PCR assays indicated the presence of the phytoplasma in the gut, fat body and salivary glands. These results indicate that ST1-C and “
Ca.
Phytoplasma vitis” have a complex life cycle in the body of
S. titanus
and are colocalized in different organs and tissues.