Characterization of Olive Associated Fungi of Cultivars with Different Levels of Resistance to Anthracnose

Olive anthracnose, caused by Colletotrichum spp., is one of the most damaging fruit diseases in olive crops worldwide. Their control is very difficult and relies mostly on the use of copper-based fungicides. The plant-associate fungal community has been increasingly recognized for playing an important role in plant health. Thus, in this work, the olive associated fungi of cultivars with different levels of resistance to anthracnose were characterized to identify potential protecting fungi for a sustainable strategy of biocontrol. A culture-dependent approach was used to assess both epiphytic and endophytic fungal communities of leaves of olive cultivars Madural (susceptible to anthracnose) and Cobrançosa (moderately tolerant), and the isolates obtained were identified by rRNA sequencing.

Overall, Ascomycota phylum and Aureobasidium genus were the most dominant, being epiphytes significantly more diverse and abundant than endophytes. The host plant (at cultivar level) had a negligible effect on the composition of fungal communities of the leaves. However, the host plant effect was found to be greater on epiphytic than on endophytic community structure. Among the genera identified in the most-resistant cultivar, Aspergillus and Pseudocercospora were the most frequently isolated within epiphytic and endophytic fungal communities, respectively; whereas in the susceptible cultivar, Aureobasidium and Didymocyrtis, were the most frequently isolated within epiphytic and endophytic fungal communities, respectively. Determination of indicator value indices has shown significant preference/specificity of a set of fungal species with the most-resistant cultivar. Future research needs to decipher these complex interactions between plant-fungi and assess their role in plant health.

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.