Role of α-Copaene in the Susceptibility of Olive Fruits to Bactrocera oleae (Rossi)

The influence of a-copaene as a fruit volatile in the susceptibility of Olea europaea L. to the olive fruit fly Bactrocera oleae (Rossi) has been investigated. By studies on the relative area of volatile components from different cultivars, a positive correlation was found between the abundance of a-copaene in the samples and the corresponding degree of fruit infestation. SPME-GC-MS analysis of volatiles from uninfested fruits of O. europaea L. cv. Serrana were performed over two years to determine the variation of a-copaene throughout the different phenological stages. The results suggested that this sesquiterpene has a significant effect on cultivar susceptibility and may act as an oviposition promoter. Further analysis by chiral GC showed that olive fruits release both a-copaene enantiomers. Bioassays on each enantiomer revealed that fruits with increased amounts of (+)-alpha-copaene favor oviposition of B. oleae females, whereas the increase of (-)-alpha-copaene affords no statistically significant differences in host preference.