Olive fruit volatiles route intraspecific interactions and chemotaxis in Bactrocera oleae (Rossi) (Diptera: Tephritidae) females

Abstract

Plant nutritional quality and chemical characteristics may affect the fitness of phytophagous insects.Here, the olfactory preferences of Bactrocera oleae (Rossi) females toward olives with different maturation and infestation status were evaluated in three cultivars: Ottobratica, Roggianella and Sinopolese. Volatile profiles from olives were identified by SPME/GC-MS. Choice tests were performed to determine the responses of B. oleae adult females toward fruits and pure chemicals linked to infestation degree. Cultivar was the main source of variability explaining the differences recorded in volatile emissions. Moreover, three VOCs [β-myrcene, limonene and (E)-β-ocimene] were associated to infestation status across all olive varieties. In choice-tests, B. oleae females always preferred the olfactory cues from low-infested over high-infested fruits. Therefore, choice-tests using synthetic VOCs, emitted in greater amount by high-infested fruit, were arranged in order to identify putative B. oleae kairomones. While females were indifferent to β-myrcene, the highest dosages of limonene and (E)β-ocimene were unfavoured by the tested flies, which preferentially moved toward the empty arm of the Y-tube. Furthermore, females preferred the lowest concentration of β-ocimene compared to the highest one. These results supported our hypothesis that fruit VOCs may serve as kairomones for female flies.Environmental conditions, food availability and ovipositional sites are crucial for phytophagous-insect survival 1,2 . The nutritional quality and the attractiveness of plants may influence the fitness of herbivores and be a key factor for oligophagous species, which can rely on a restricted number of host-plants 3,4 . Therefore, the recognition of suitable ovipositional sites is critical for several fruit flies 5,6 .Bactrocera oleae (Rossi) (Diptera: Tephritidae), commonly known as the olive fruit fly, is a strictly monophagous pest, which can feed exclusively on Olea species. The larval stages feed and develop solely inside olive drupes, excavating galleries inside the pulp. The fully developed larvae open an exit hole on the olive surface and usually pupate outside the fruit. During the oviposition process, B. oleae females carefully choose suitable fruit for oviposition, either performing aggressive behaviours toward conspecifics to gain and maintain the oviposition site 7 . In the Mediterranean area, the olive fruit fly population commonly increases during summer season until the harvest period. Depending on climate conditions, B. oleae produce from 2 to 7 generations during the favourable season, although this fly can reproduce also during winter in mild climates 8 . The olive fruit fly is considered the key pest of olive crop (Olea europea L.), causing great qualitative and quantitative yield loses, as well as premature fruit drop. The presence of ovipositional puncture and/or active infestation can decrease or even nullify the value of table olives and seriously reduce oil yield and quality 9,10 . Furthermore, the olive frui...

Drupe Characters, Fatty Acids, Polyphenolic and Aromatic Profile of Olive Oil Obtained from “Oliva Bianca”, Minor Autochthonous Cultivar of Campania

“…The most present compounds were trans-2-hexenal that represented 72.30% of total VOCs, trans-2-hexen-1-ol (7.75%), hexanol (3.34%), ethanol (2.93%), ethyl acetate (3.60%), 1-penten-3-one (2.52%), ethyl-1,5-octadiene (1.83%) and β-ocimene. Compounds that were present below 1% were (t, t) 2,4-hexadienal, 4,8-dimethyl-1,7-nonadiene, cis-3-hexenyl acetate, nonanal, 1,7-octadien-3-one, 2 methyl-6-methylene and α-cubebene, which have also been found in other oils deriving from different cultivars and that influence the flavor of olive oil [14][15][16][17][18][19][20].…”

“…This aldehyde is derived from the metabolism of α-linolenic acid through the lipoxygenase (LOX) pathway, which influences the taste of green, pungent, bitter fruity, apple, almond and cut grass [40,41]. Trans-2-hexen-1-ol has green and pungent notes and an odor described as banana-green deriving from the reduction trans-2-hexenal by alcohol dehydrogenase (ADH) [18,20]. Hexanol influences the flavor of green fruity, floral and alcoholic [15,18], it originated from hexanal through ADH activity [41].…”

“…Ethyl-1,5-octadiene gives a smell of green and it is also detected in slightly rancid and moldy oils [15,44]. β-ocimene in oils derived from fruits infested with Bactrocera oleae [16,20] but it was also detected in filtered and unfiltered oil of cultivar Ravece [45] and its concentration was influenced by pedoclimatic conditions [46]. Methyl benzoate affects a pungent and greasy taste [18,19,44].…”

Tephritid Fruit Fly Semiochemicals: Current Knowledge and Future Perspectives

“…Currently used setups adopted for the study of tephritid olfaction include (i) two-choice systems, (ii) flight tunnels, and (iii) multi-arm olfactometers. Two-choice systems, using arenas (i.e., observation chambers) [ 174 , 318 , 319 ], as well as Y-tubes/T-maze [ 85 , 231 , 293 , 320 ], have been used to evaluate attractive or repulsive responses following exposure to pheromone (isolated from headspace or rectal glands); in this framework, dynamic systems like the Y-tubes, allowing an air flow carrying the chemicals to be evaluated for the chemo-ecological role should be preferred, since they avoid the risk of saturating receptors of the tested flies, which is common in still-air arenas. Flight tunnels, also known as wind tunnels, are extremely useful to monitor medium-distance flight responses to mate-derived chemicals [ 201 , 270 , 321 ].…”

Volatile Infochemicals from Rhyzopertha dominica Larvae and Larval Feces Involved in Theocolax elegans Host Habitat Location

“…Fourteen volatile compounds emitted by the various tested substrates were identified by GC-MS analysis following the method by Giunti et al [37] (Table 3). Specifically, 10 volatile compounds were detected from undamaged wheat samples, while 12 VOCs infested wheat ones.…”