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The grape endophytic microbiome and its impact on Pierce's disease development
P. E. ROLSHAUSEN (1), J. I. Yang (2), P. Ruegger (1), J. Borneman (1), C. Roper (1). (1) University of California, Riverside, CA, U.S.A.; (2) National Taiwan University, Taipei, CA, Taiwan

Pierce’s Disease (PD) of grapevine, caused by <i>Xylella fastidiosa</i> (<i>Xf</i>), poses a major threat to the grape industry. Interestingly, in vineyards that are heavily infected with PD, there are examples of vines exhibiting either no symptoms or very mild PD symptoms (disease-escaped). All vines in a vineyard are clonal so the differences in tolerance to PD are likely not attributed to the genetics of the plant. We hypothesize that the xylem-inhabiting microorganisms in these disease-escaped vines are inhibiting <i>Xf</i> and reducing disease severity, due to their shared ecological niche. The goal of this project is to characterize the microbial communities residing in PD-infected vines and compare them to disease-escaped vines to identify beneficial organisms antagonistic to <i>Xf</i>. Fungal and bacterial endophytic communities were characterized using an Illumina MiSeq platform targeting the ITS and 16S rRNA genes, respectively. Pseudomonadales was the most abundant bacterial taxonomic group, and Pleosporales and Sordariales were the most abundant fungal taxonomic groups. Some phylotypes correlated either positively or negatively with PD severity. Furthermore, we identified a subset of culturable microbes that possessed strong anti-<i>Xf</i> properties and suppressed PD symptom development in greenhouse bioassays. We envision harnessing these microbes to construct a beneficial synthetic phytobiome that can be deployed into grapevines trees during the nursery propagation process.

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