Fruit-associated endophytes from olive cultivars with different levels of resistance to fruit fly and their relationship with pest infestation

Olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae) is the most important olive pest and with a major economic importance in the olive production worldwide. Different olive cultivars exhibit different propensities to fruit fly infestation and the causes are still unclear. Here, we want to disclose the potential role of the olive-associated endophytes in conferring such susceptibility differences. Accordingly, the endophytic microbial composition of infested and non-infested fruits from cultivars Madural (susceptible to olive fly) and Cobrançosa (less susceptible) were studied. A culture-dependent approach was used, being the isolates identified by sequencing of their internal transcribed spacer (for fungi) and 16S rRNA gene regions (for bacteria). Overall, there was a larger consortium of bacteria associated to olives than fungi. The bacterial communities were predominantly composed of Proteobacteria and Actinobacteria phyla while the fungal isolates belong to the Ascomycota and Basidiomycota. Both host cultivar and level of fly infestation had a negligible effect on fungal and bacterial community composition. Despite this, it was found a clear positive association of microbial consortia with the resistant cultivar (Kocuria sp., Actinobacterium sp., Rhodococcus sp., Pseudomonas citronellolis, Aspergillus flavus, Cladosporium sp., and Meristemomycetes arctostaphylos) and non-infested fruits(Kocuria sp., Stereum sp., and Vishniacozyma victoria). Their function roles on host cultivar susceptibility/resistance to fruit fly is a topic that requires further studies.

Acknowledgements: 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.