Olive anthracnose, mainly caused by Colletotrichum acutatum, is considered a key biotic
constraint of the olive crop worldwide. This work aimed to evaluate the ability of the endophytes
Aureobasidium pullulans and Sarocladium summerbellii isolated from olive trees to reduce C. acutatum
growth and anthracnose symptoms, and to assess A. pullulans-mediated changes in olive fruit
volatile organic compounds (VOCs) and their consequences on anthracnose development. Among
the endophytes tested, only A. pullulans significantly reduced the incidence (up to 10-fold) and
severity (up to 35-fold) of anthracnose in detached fruits, as well as the growth (up to 1.3-fold),
sporulation (up to 5.9-fold) and germination (up to 3.5-fold) of C. acutatum in dual culture assays.
Gas chromatography–mass spectrometry analysis of olives inoculated with A. pullulans + C. acutatum
and controls (olives inoculated with C. acutatum, A. pullulans or Tween) led to the identification
of 37 VOCs, with alcohols being the most diversified and abundant class. The volatile profile
of A. pullulans + C. acutatum revealed qualitative and quantitative differences from the controls
and varied over the time course of microbial interactions. The most significant differences among
treatments were observed at a maximal reduction in anthracnose development. At this stage, a set of
VOCs, particularly Z-3-hexen-1-ol, benzyl alcohol and nonanal, were highly positively correlated
with the A. pullulans + C. acutatum treatment, suggesting they play a critical role in anthracnose
reduction. 6-Methyl-5-hepten-2-one and 2-nonanone were positively associated with the C. acutatum
treatment and thus likely have a role in pathogen infection.
This research was funded by FEDER funds through COMPETE (Operational Programme
for Competitiveness Factors) and by the Foundation for Science and Technology (FCT, Portugal)
within the POCI-01-0145-FEDER-031133 (MicOlives, PTDC/ASP-PLA/31133/2017) project, as well
as the Mountain Research Center—CIMO (UIDB/00690/2020).
