Characterization of the microflora associated to Scaphoideus titanus, the insect vector of the "flavescence dorée"

Several wine production areas in Europe are afflicted by "flavescence dorée" (FD), a grape yellows caused by 'Candidatus Phytoplasma vitis', transmitted by the phloem-feeder leafhopper Scaphoideus titanus Ball (Hemiptera Cicadellidae). Symbiotic control of disease transmission, exploiting natural symbionts of the vector, could represent an innovative strategy against FD diffusion. A study was conducted to characterize the microflora associated to S. titanus specimens, collected from FD-contaminated vineyards in the Italian region of Piedmont. By length heterogeneity PCR we identified a major peak associated with almost all the individuals examined. Characterization by denaturing gradient gel electrophoresis confirmed the presence of a major band corresponding to sex-ratio-distorting endosymbionts of the 'Candidatus Cardinium hertigii' group; electron microscopy of tissues of S. titanus showed bacterial cells with the typical morphology of 'Ca. Cardinium hertigii' together with cell morphologies resembling those of 'Ca. Phytoplasma vitis'. Our findings suggest that this endosymbiont, named ST1-C, described for the first time in Cicadellidae, is transovarially transmitted and could have a complex life cycle in the insect body; in addition it colocalizes with 'Ca. Phytoplasma vitis' several host tissues. These results make ST1-C an interesting candidate for the symbiotic control of FD diffusion.