Understanding fungal communities of olive tree leaves for application to climate change adaptation

The olive tree (Olea europaea subsp. europaea L.) is a typical plant of the Mediterranean vegetation, well adapted to drought and poor soils being also tolerant to high solar irradiance. The phyllosphere microbiota associated with these plants is likely to play a role in their tolerance to such harsh environmental conditions. Here, we have characterized the endophytic and epiphytic fungal community present in leaves of olive trees, for potential application of these insights to climate change adaptation. Leave samples were collected in two rainfed olive orchards near Mirandela (NE Portugal), a Mediterranean type climate region with typical short, hot, dry, and mostly clear summers and cold to very cold, wet winters. Fungi were isolated from the surface and inner tissues of leaves. The isolates obtained were identified by ITS rRNA gene sequencing and their phylogenetic diversity was then analyzed. Strains were phylogenetically placed all across the fungal tree of life, which make evident the high diversity of fungi associated with olive tree leaves. At higher taxonomic ranks, Ascomycota was the more abundant phylum either for endophytes (82.6%) or epiphytes (95.6%), while Dothideomycetes (41.1% and 53.2%, respectively) was the most abundant class which includes the order Pleosporales (19.3% and 25.4%). A Celerioriella-like species and two unassigned species belonging to Phaeomoniellaceae and Pleosporineae were the most abundant taxa within 23 species (out of 161) found in both epiphytic and endophytic subsamples. These strains are good candidates to be studied for their resilience to climate changes in order to be applied as "tolerance inducers" in olive crops from this Mediterranean area.

Acknowledgments: This work is supported by FEDER funds through the COMPETE (Operational Programme for Competitiveness Factors) and by National funds through the FCT (Foundation for Science and Technology) within the POCI-01-0145-FEDER-031133 (MicOlives) project.