Volatile fingerprints of sweet oranges infested by three fruit fly species and their potential for detection of infestation.

Abstract

Gas chromatography-mass spectrometry was used to characterize volatile organic compounds (VOCs) emitted by sweet oranges ('Washington Navel') infested by Ceratitis capitata, Bactrocera dorsalis, and Bactrocera zonata across larval developmental stages. From 195 samples, 79 VOCS were identified. Infested fruits released substantially higher total VOCs than controls, mainly due to strong increases in terpenes and terpenoids. Emissions peaked immediately after oviposition and changed in a species-specific manner during larval development. Multivariate analyses revealed clear metabolic alterations. Principal component analysis indicated partial separation between infested and non-infested fruits, while permutational multivariate analysis of variance confirmed significant differences. Orthogonal partial least squares discriminant analysis and variable importance in the projection scores highlighted key compounds, including (E)-β-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene, β-myrcene, and limonene. Sparse partial least squares discriminant analysis identified species-specific markers for early Ceratitis capitata, Bactrocera dorsalis, and late-stage Bactrocera zonata. These findings demonstrate that VOC fingerprints enable early-stage, non-destructive detection of tephritid infestation.

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