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The genus Arsenophonus (Gammaproteobacteria) is comprised of intracellular symbiotic bacteria that are widespread across the arthropods. These bacteria can significantly influence the ecology and life history of their hosts. For instance, Arsenophonus nasoniae causes an excess of females in the progeny of parasitoid wasps by selectively killing the male embryos. Other Arsenophonus bacteria have been suspected to protect insect hosts from parasitoid wasps or to expand the host plant range of phytophagous sap-sucking insects. In addition, a few reports have also documented some Arsenophonus bacteria as plant pathogens. The adaptation to a plant pathogenic lifestyle seems to be promoted by the infection of sap-sucking insects in the family Cixiidae, which then transmit these bacteria to plants during the feeding process. In this study, we define the specific localization of an Arsenophonus bacterium pathogenic to sugar beet and strawberry plants within the plant hosts and the insect vector, Pentastiridius leporinus (Hemiptera: Cixiidae), using fluorescence in situ hybridization assays. Phylogenetic analysis on 16S rRNA and nucleotide coding sequences, using both maximum likelihood and Bayesian criteria, revealed that this bacterium is not a sister taxon to "Candidatus Phlomobacter fragariae," a previously characterized Arsenophonus bacterium pathogenic to strawberry plants in France and Japan. Ancestral state reconstruction analysis indicated that the adaptation to a plant pathogenic lifestyle likely evolved from an arthropod-associated lifestyle and showed that within the genus Arsenophonus, the plant pathogenic lifestyle arose independently at least twice. We also propose a novel Candidatus status, "Candidatus Arsenophonus phytopathogenicus" novel species, for the bacterium associated with sugar beet and strawberry diseases and transmitted by the planthopper P. leporinus.

Grapevine leafroll is one of the most widespread virus diseases of grapevine and Grapevine leafrollassociated virus 3 (GLRaV-3) is one of its major causal agents. The effect of GLRaV-3 elimination was studied under vineyard conditions for two years by comparing the virus-free and infected lines of the same clone of Vitis vinifera cv. Dolcetto, an important red wine cultivar grown in northwestern Italy. The results confirmed the advantages of using virus-free vines in terms of field performance (vigor, yield, leaf photosynthesis, and juice soluble solids), whereas the advantages in wine quality were less evident. Sensory analysis clarified that the wine from virus-free vines was slightly different from that of vines infected by GLRaV-3, but did not indicate a significant preference for one or the other.

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