| Resumo: | Xylella fastidiosa is a plant pathogen transmitted by insect vectors that cause high losses in a variety of agriculturally important crops. In Europe, an outbreak of X. fastidiosa was first detected in 2013 in olive trees in Southern Italy, being Philaenus spumarius (L.) identified as the vector involved in this outbreak. In this work, as a first approach, we explored the endophytic microbial community inhabiting plants in order to design new approaches to manage the X. fastidiosa in the olive tree and its insect vector. Nymphs of P. spumarius feeds commonly on stems of Coleostephus myconis (L.), which is a common weed found in olive groves. A better understand of the feeding effect on the fungal community residing in this weed and of the role of these fungi in feeding choice could assist in the manipulation of P. spumarius populations. For this, the endophytic fungal community of stems, leaves and inflorescences of C. myconis with three levels of P. spumarius infestation was studied by cultural dependent method. Feeding was showed to affect the fungal communities in the stem and leaf but not the ones in the inflorescence. A set of fungi was identified to be associated to either infested or non-infested plants, suggesting playing a key role on the feeding process. As a second approach, it was observed, in the outbreak, the presence of olive cultivars resistant (cv. FS17) or susceptible (cv. Kalamata) to X. fastidiosa. The study of the xylem microbiome of these two cultivars, was performed through Illumina amplicon sequencing in order to determine whether susceptibilities differences are linked to its core microbiome. Overall, the core microbiome was dominated by members of the Proteobacteria (81% of the total bacteria reads) and Ascomycota (98% of the total fungal reads). In non-infected trees, the core microbiome was found to differ between susceptible and resistant cultivars. The presence of X. fastidiosa showed to induce greater variation in microbial composition and diversity of the susceptible cultivar than of the resistant cultivar. Specific fungal/bacterial signatures were detected to either the presence or the absence of X. fastidiosa in the xylem vessels, suggesting an important role of these microorganisms in pathogen establishment/development. Our study provides microbial candidates to further evaluate their role in the management of P. spumarius and X. fastidiosa.
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