Characterization and variation of bacterial and fungal communities from the sapwood of Apulian olive varieties with different susceptibility to Xylella fastidiosa

Endophytes are symptomless fungal and/or bacterial microorganisms found in almost all living plant species. The symbiotic association with their host plants by colonizing the internal tissues has endowed them as a valuable tool to suppress diseases, to stimulate growth, and to promote stress resistance. In this context, the identification of cultivable endophytes residing the sapwood of Apulian olives might be a promising control strategy for xylem colonizing pathogens as Xylella fatidiosa. To date, olives sapwood cultivable endophytes are still under exploration; therefore, this work pursues a study of diversity and occurrence variation of cultivable endophytes in the sapwood of different olive varieties under the effect seasonality, geographical coordinates, and X. fastidiosa infection status. Briefly, our study confirms the stability of sapwood cultivable endophytic communities in the resistant olive variety, presents the seasonal and geographical fluctuation of olives sapwood endophytes, describes the diversity and occurrence frequency of fungal and bacterial genera, and finally retrieves some of sapwood-inhabiting fungal and bacterial isolates are known as biocontrol agents of plant pathogens. Thus, the potential role of these bacterial and fungal isolates in conferring olive tree protection against X. fastidiosa should be further investigated.