# The Infestation of Olive Fruits by _Bactrocera oleae_ ([PERSON])
## 2 Results and Discussion  
### Effect of B. oleae Infestation on the Volatile Profile of VOO  
Olive fruit infestation by _B. oleae_ affects the volatile profile of the oils of Picul, Manzanilla, and Hoijblanca cultivars (Figure 1), producing significant changes both in the main families of volatile components of VOO (Table S1) and in some individual compounds with very different chemical/biochemical origins influencing the VOO aroma (Table S2). It is well known that oils from different olive genotypes exhibit a high level of variability regarding their volatile profiles [26]. Thus, the oils obtained from sound, non-infested, olive fruits from the three cultivars studied showed very different contents of C6 and C5 compounds (Figure 1). Hoijblanca oils had the highest content in C6 aldehydes derived from LNA (aldehydes C6/LnA) and LA (aldehydes C6/LA), as well as of LOX-derived esters, whereas Picul oils exhibited the highest content of C5 carbonyls derived from LA (carbonyls C5/LnA), and Manzanilla oils showed the highest contents of C5 alcohols derived from the same acid (alcohols C5/LnA). Despite these cultivar differences, a common pattern was observed in the volatile profiles of the oils obtained from _B. oleae_ infested fruits. Thus, a statistically significant increase (\(p\leq 0.05\)) in the content of C6/LnA was observed in the three cultivars, the most important group of volatile compounds produced through the LOX pathway (Supplementary Table S2). More specifically, the rise observed in the content of C6/LnA compounds of Manzanilla oils obtained from _B. oleae_ infested fruits was around 15%, while the increments observed in Picul and Hoijblanca were around 50%. These data support previous findings on the increase of C6 volatiles as a consequence of plant-insect interaction [27]. In the three cultivars, the increases in the content of C6/LnA compounds were mainly due to the strong increase observed in the production of (_E_)-hex-2-enal, the most qualitatively and quantitatively relevant compound for VOO aroma due to its high concentration in most olive oils and its relatively low odor threshold [25; 26]. Thus, the content of (_E_)-hex-2-enal in oils produced from _B. oleae_-infested Manzanilla fruits was double that of control oils, while the concentration of this compound in oils from infested Picul and Hoijblanca fruits tripled that of the control oils (Table S3). These results agree with those reported by [PERSON] et al. [11], who found that olive fruits from cvs. Leccino and Coratina infested with _B. oleae_ larvae emitted higher amounts C6 aldehydes. These authors also  
Figure 1: Content (ng g\({}^{-1}\) oil) of the main groups of volatile compounds in oils extracted from infested (I) and non-infested (C) olive fruits (cvs. Picul, Manzanilla, and Hoijblanca). Data are mean contents from three different analyses. observed the increase in the content of other volatile compounds, such as nonanal, acetic acid, and ethanol. However, we did not find significant increases in the content of nonanal in oils from infested fruits. The presence of this compound in VOO is exclusively associated with chemical oxidation processes, since its formation in olives cannot be linked to the LOX pathway, as it occurs in other fruits, given that olive HPL is strictly specific for 13-hydroperoxides and nonanal is formed by cleavage of 9-hydroperoxides [14]. We also observed a similar increase in the content of (_E_)-hex-2-eral after inoculation of Picul alive trees with the fungus _V. dahliae_, going from 66% of the content of C6/LnA compounds in control oils to 80% in oils from infested trees [25]. On the contrary, the pathogen _V. dahliae_ caused a significant decrease in the content of C5/LnA compounds that we have not found in oils produced from fruits attacked by _B. oleae_-infested fruits. These differences could be explained by the induction of specific and different defense systems against pathogens and insects.