Do endophytes play a role in the olive tree susceptibility to fruit fly infestation?

Abstract: Olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is the most important olive pest worldwide, by damaging olives due to oviposition and drastically decreasing the crop yield. In Portugal, it has been found that different olive cultivars exhibited different propensities to fruit fly infestation, being the cv. Cobrançosa less susceptible than the cv. Madural. This work aims to disclose the role play by fruit-associated endophytes in conferring these different host plant susceptibilities to fruit fly infestation. Accordingly, the endophytic microbial composition of infested ad non-infested fruits from cultivars Cobrançosa and Madural were studied, by using a culture dependent PCR-based identification approach. Overall, 61 operational taxonomic units (OTUs) were obtained, being identified until the species/genera level a total of 21 bacteria and 23 fungi. The bacterial community was mostly composed by members of phyla Proteobacteria and genus Pseudomonas, while fungal community was dominated by Ascomycota and Sarocladium members. No significant differences were observed on the diversity of endophytes among the two cultivars or infestation level. Still, distinct endophyte community’s composition was detected among cultivars, being this factor explaining 2.1 % and 2.3 % of bacterial and fungal composition variation, respectively. Endophytic communities from infested and non-infested fruits also differs significantly, but with greater differences in the most susceptible cv. Madural than in cv. Cobrançosa. Specific bacterial/fungal taxa were found to be positively associated to the most resistant cultivar and non-infested fruits. Their potential role in conferring host plant protection against olive fly attack will be discuss.

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