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Electrophysiological response of Bactrocera oleae (Rossi) (Diptera: Tephritidae) adults to olive leaves essential oils from different cultivars and olive tree volatiles

Publication . Malheiro, Ricardo; Ortiz, Antonio; Casal, Susana; Baptista, Paula; Pereira, J.A.

In the present study, the electrophysiological response of olive fly adults, Bactrocera oleae (Rossi), to oliveleaves essential oils (EO’s) from different cultivars (cvs. Cobrançosa, Madural and Verdeal Transmontana) with distinct fly susceptibility degrees, as well as host volatiles ([(E)-2-hexenal, α-pinene, farnesene, xylene, and nonanal]) and semiochemicals (spiroketal, and (Z)-9-tricosene) were assessed at differentadults ages ([0–5] days old, early young adults; [5–10] days old, corresponding to sexual maturity; and[10–15] days old, when females are gravid).Results showed clear differences in the EAG response of both sexes to EO’s of the different cultivars, with higher signal in cv. Cobrançosa, the less susceptible to olive fly. An inverse proportionality was found between the EAG response to EO’s in both sexes and the susceptibility degrees to olive fly. Chemical composition of EO’s proved to be highly influenced by olive cultivars, with a clear differentiation between them. A possible deterrent mechanism could be involved in the observed results. Host volatiles, mainly (E)-2-hexenal and nonanal exerted higher EAG responses, (E)-2-hexenal mainly in females at sexual maturity and oviposition period, while nonanal elicited higher responses at [5–10]days old in males, corresponding to sexual maturity. The present results give important results regarding olive fly oviposition preference as well to olive fly-olive tree interactions.

2015Journal article

Restricted access

Caracterização da fração volátil de azeitonas representativas da região de Trás-os-Montes: cvs. Cobrançosa, Madural e Verdeal Transmontana

Publication . Malheiro, Ricardo; Casal, Susana; Cunha, Sara C.; Petisca, C.; Baptista, Paula; Bento, Albino; Pereira, J.A.

A fracção volátil das matérias-primas exerce um papel fundamental tanto na qualidade final dos produtos alimentares bem como no que diz respeito à sua aceitabilidade por parte do consumidor. Em Trás-os-Montes, uma região com forte tradição olivícola, a qualidade dos produtos do olival (azeite, azeitonas de mesa e pastas de azeitona) passa indiscutivelmente pela fracção volátil dos mesmos, sendo o factor varietal preponderante. Neste sentido, pretendeu-se caracterizar a fracção volátil das três cultivares de azeitona mais representativas de Trás-os-Montes (Cvs. Cobrançosa, Madural e Verdeal Transmontana) por HS-SPME e GC/MS. A azeitona foi colhida próximo do momento óptimo de colheita (índice de maturação = 3; 3ª semana de Outubro 2011), com 5 lotes por cultivar. As diferentes cultivares influenciaram tanto qualitativamente como quantitativamente a fracção volátil das azeitonas, tendo estas sido caracterizadas maioritariamente por hidrocarbonetos (tolueno), álcoois ((Z)-3-hexen- 1-ol e 1-hexanol), aldeídos (hexanal, heptanal, benzaldeído, nonanal, decanal), ésteres ((Z)-3-hexen-1-ol acetato), cetonas (6-metil-5-hepten-2-ona), monoterpenos (α-pineno, limoneno, L-mentol) e sesquiterpenos ((+)- ciclosativeno, α-copaeno, α-muuroleno). Os hidrocarbonetos, álcoois e aldeídos foram as classes químicas presentes com maior abundância, sendo o tolueno, o (Z)-3-hexen-1-ol e o nonanal os voláteis mais abundantes. O (Z)-3-hexen-1-ol juntamente com o hexanal estão associados a sensações verdes e a erva, característica sensorialmente considerada como um atributo. A fracção volátil é específica de acordo com a variedade de azeitona em estudo. Um aspecto a ter em conta a quando da elaboração de produtos à base de azeitona, tendo em vista também a aceitabilidade por parte do consumidor.

2014Conference paper

Open access

Olive cultivar and maturation process on the oviposition preference of Bactrocera oleae (Rossi) (Diptera: Tephritidae)

Publication . Malheiro, Ricardo; Casal, Susana; Pinheiro, Lara Alina; Baptista, Paula; Pereira, J.A.

The olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a key-pest in the main olives producing areas worldwide, and displays distinct preference to different olive cultivars. The present work intended to study oviposition preference towards three Portuguese cultivars (Cobrançosa, Madural, and Verdeal Transmontana) at different maturation indexes. Multiple oviposition bioassays (multiple-choice and no-choice) were conducted to assess cultivar preference. No-choice bioassays were conducted to assess the influence of different maturation indexes (MI 2; MI 3, and MI 4) in single cultivars. The longevity of olive fly adults according to the cultivar in which its larvae developed was also evaluated through survival assays.Cultivar and maturation are crucial aspects in olive fly preference. Field and laboratory assays revealed a preference towards cv. Verdeal Transmontana olives and a lower susceptibility to cv. Cobrançosa olives. A higher preference was observed for olives at MI 2 and MI 3. The slower maturation process in cv. Verdeal Transmontana (still green while the other cultivars are reddish or at black stage) seems to have an attractive effect on olive fly females, thus increasing its infestation levels. Olive fly adults from both sexes live longer if emerged from pupae developed from cv. Verdeal Transmontana fruits and live less if emerged from cv. Cobrançosa. Therefore, olive cultivar and maturation process are crucial aspects in olive fly preference, also influencing the longevity of adults.

2019Journal article

Open access

Identification of leaf volatiles from olive (Olea europaea) and their possible role in the ovipositional preferences of olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae)

Publication . Malheiro, Ricardo; Casal, Susana; Cunha, Sara C.; Baptista, Paula; Pereira, J.A.

The olive fly, Bactrocera oleae (Rossi), is a monophagous pest that displays an oviposition preference among cultivars of olive (Olea europaea L.). To clarify the oviposition preference, the olive leaf volatiles of three olive cultivars (Cobrançosa, Madural and Verdeal Transmontana) were assessed by headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC/MS) at six different periods of olive fruit maturation and degrees of infestation. A total of 39 volatiles were identified, mainly esters and alcohols, with a minor percentage of aldehydes, ketones and terpenic compounds, including sesquiterpenes. At sampling dates with higher degrees of infestation, cv. Cobrançosa had, simultaneously, significantly lower infestation degrees and higher volatile amounts than the other two cultivars, with a probable deterrent effect for oviposition. The green leaf volatiles (GLVs) (Z)-3-hexen-1-ol and (Z)-3-hexen-1-ol acetate) were the main compounds identified in all cultivars, together with toluene. The abundance of GLVs decreas ed significantly throughout maturation, without significant differences among cultivars, while toluene showed a general increase and positive correlation with olive fly infestation levels. The results obtained could broaden our understanding of the roles of various types and amounts of olive volatiles in the environment, especially in olive fly host selection and cultivar preference.

2016Journal article

Open access

Physico-chemical characteristics of olive leaves and fruits and their relation with Bactrocera oleae (Rossi) cultivar oviposition preference

Publication . Malheiro, Ricardo; Casal, Susana; Baptista, Paula; Pereira, J.A.

Bactrocera oleae (Rossi) (Diptera: Tephritidae) oviposition preference to Portuguese olive cultivars with different susceptibilities (cvs. Cobrançosa, Madural, and Verdeal Transmontana) was studied by physical and chemical parameters. Physical parameters, maturation indices, infestation levels, and fatty acids profiles were recorded.Verdeal Transmontana olives revealed higher susceptibility to olive fly attack, while cv. Cobrançosa was the less affected cultivar. A faster maturation in cv. Cobrançosa and a slower one in cv. Verdeal Transmontana were observed. Verdeal Transmontana olives reported higher volume and lower elongation, while both olives and leaves reported higher lightness, all possible attractive cues for olive fly. Fatty acids composition revealed a characteristic profile in each cultivar with constant differences during crop season.Overall, maturation process influenced biometrical data and color of olive cultivars. The slower maturation process characteristic from cv. Verdeal Transmontana could modulate the composition and physical appearance of olives, therefore interfering with olive fly females oviposition preference.

2015Journal article

Open access