The -Resistant Olive Cultivar "Leccino" Has Stable Endophytic Microbiota during the Olive Quick Decline Syndrome (OQDS).

is a highly virulent pathogen that causes Olive Quick Decline Syndrome (OQDS), which is currently devastating olive plantations in the Salento region (Apulia, Southern Italy). We explored the microbiome associated with -infected (-infected) and -uninfected (-uninfected) olive trees in Salento, to assess the level of dysbiosis and to get first insights into the potential role of microbial endophytes in protecting the host from the disease. The resistant cultivar "Leccino" was compared to the susceptible cultivar "Cellina di Nardò", in order to identify microbial taxa and parameters potentially involved in resistance mechanisms. Metabarcoding of 16S rRNA genes and fungal ITS2 was used to characterize both total and endophytic microbiota in olive branches and leaves. "Cellina di Nardò" showed a drastic dysbiosis after infection, while "Leccino" (both infected and uninfected) maintained a similar microbiota. The genus dominated all "Leccino" and -uninfected "Cellina di Nardò" trees, whereas prevailed in infected "Cellina di Nardò". Diversity of microbiota in -uninfected "Leccino" was higher than in -uninfected "Cellina di Nardò". Several bacterial taxa specifically associated with "Leccino" showed potential interactions with . The maintenance of a healthy microbiota with higher diversity and the presence of cultivar-specific microbes might support the resistance of "Leccino" to . Such beneficial bacteria might be isolated in the future for biological treatment of the OQDS.