Abstract
The olive fly, Bactrocera oleae (Rossi), a serious threat to the olive crop worldwide, displays ovipositon preference for some olive cultivars but the causes are still unclear. In the present work, three Portuguese olive cultivars with different susceptibilities to olive fly (Cobrançosa, Madural, and Verdeal Transmontana) were studied, aiming to determine if the olive volatiles are implicated in this interaction. Olive volatiles were assessed by SPME-GC-MS in the three cultivars during maturation process to observe possible correlations with olive fly infestation levels. Overall, 34 volatiles were identified in the olives, from 7 chemical classes (alcohols, aldehydes, aromatic hydrocarbons, esters, ketones, sesquiterpenes, and terpenes). Generally, total volatile amounts decrease during maturation but toluene, the main compound, increased in all cultivars, particularly in those with higher susceptibility to olive fly. Sesquiterpenes also raised, mainly α-copaene. Toluene and α-copaene, recognized oviposition promoters to olive fly, were correlated with the infestation level of cvs. Madural and Verdeal Trasnmontana (intermediate and highly susceptible cultivars respectively), while no correlations were established with cv. Cobrançosa (less susceptible). No volatiles with inverse correlation were observed. Volatile composition of olives may be a decisive factor in the olive fly choice to oviposit and this could be the basis for the development of new control strategies for this pest.
Highlights
Olea europaea L. has registered a considerable growth and dissemination worldwide in the last decades, attracting the attention of new producing countries worldwide
The main objective of this work was to characterize the volatile fraction of the olives during ripening by headspace solid-phase microextraction (HS-SPME)-Gas chromatography-mass spectrometry (GC-MS), while trying to establish possible relations between infestation levels observed on each cultivar with the volatiles of the drupes
In light of the obtained results, it is clear that olive fly has an oviposition preference for cv
Summary
Olea europaea L. has registered a considerable growth and dissemination worldwide in the last decades, attracting the attention of new producing countries worldwide. Productive records are being registered since the beginning of this decade, exceeding for the first time the 20 million tons barrier (20.4 million tons of olives in 2011; 20.3 million tons in 2013; [1]) Escorting such dissemination, the dispersion of Bactrocera oleae (Rossi) (Diptera: Tephritidae), the olive fly, is verified, being a key pest of olives worldwide, with special importance in the Mediterranean region [2]. The dispersion of Bactrocera oleae (Rossi) (Diptera: Tephritidae), the olive fly, is verified, being a key pest of olives worldwide, with special importance in the Mediterranean region [2] This dipteran causes severe olive production losses due to fruit drop [3], leads to the production of low quality olive oils [4], and olives infected by this pest cannot be used for table olives processing. Pests and diseases are believed to reduce olives production by 15% on average [7], which means that about 3.6 million tons of olives were wasted in 2013, with olive fly being responsible for tremendous share in this loss
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