ESTRUCTURA ORGANIZACIONAL

1.3.1 Mediterranean fruit fly C. capitata volatiles

The volatiles produced by the Mediterranean fruit fly, C. capitata, a serious citrus plant pest are important in understanding the communication between males and females (Jacobson et al., 1973). Various chemicals play a role in the intraspecific communication of fruit flies that involve more chemicals profile classes (Tumlinson, 1989). Several techniques have been used to identify medfly volatiles (Cossé et al., 1995). There are 56 compounds (from a total of 69) from the calling, sexually mature, laboratory-reared males of the medfly, C. capitata. These compounds were contained in methyl and ethyl hexenoates and hexanoates, C4‐C6 esters and/or

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acetates, ethyl and methyl octenoates, monoterpenes, sesquiterpenes, C2‐C5 acetates, alcohols

and ketones (Jang, 1995). Baker et al. (1985) reported that the volatiles emitted by the sexually mature male medfly C. capitate had been identified and the key component of interest in the sexual attraction of virgin female to male flies was demonstrated to be the novel sex pheromone 3,4-dihydro-2H-pyrrole. Light et al. (1992) identified six‐carbon unsaturated aldehydes, alcohols, methyl, ethyl hexanoates, octanoates, hexenyl acetates, monoterpenes, acetates, alcohols and lactones from both male and female C. capitata under laboratory conditions. Flath et al. (1993) studied the effect of fly age and time of day on volatiles emissions from the male of medfly C. capitata. They collected the samples for three different ages and across three different times. They found that 32 components were identified the; four that previously had not been reported include propan-2-01, hexanal, phenol, and (28)-a-farnesenel, and three others had only partially been identified in an earlier study: prop-2-yl (E)-octenoate, ethyl (E)-a- octenoate, and propyl (E)-3-octenoatel. (E)-2-hexenoic acid was also a major component; however, it was not as readily quantified. The most abundant emission components were ethyl (E)-&octenoate, ethyl acetate, geranyl acetate, 1-pyrroline and (E,E)-a-farnesene from 5-6- and 11-12-day-old flies. Heath et al. (1991) analysed the three major components of male Mediterranean fruit fly sex pheromones ethyi-(E)-3-octenoate, geranyl acetate, and (E,E)-α- farnesene in the laboratory and among reared wild male medflies. They found that the three emitted compounds formulate a synthetic blend that releases the compounds in a ratio similar to that released by wild male medflies. Jacobson et al. (1973) identified the sex pheromones of the male medfly C. capitata. They collected these via air condensation, and they were identified, and separated in pure form as methyl (E) 6-nonenoate, and (E)-6-nonen-l-ol.

According to Cossé et al. (1995), α-farnesene, is a common component of the male pheromone of male C. capitata. Methyl octanoate compounds have been identified in the pheromones of male medflies and are released by calling males (Gonçalves et al., 2006; Wicker-Thomas, 2007). Methyl hexanoate and methyl esters were implicated in medfly intraspecific communication (Warthen et al., 1997). Linaloo 1,2,3-dimethylpyrazine, 2,5-dimethylpyrazine, and geranyl acetate were used to synthesise the chemicals of the sex pheromones of male C. capitata (Baker et al., 1990). Ethyl hexanoate, α-trans-bergamotene, 2-heptanone, 2,5- dimethylpyrazine, 3-octanone, limonene, methyl heptanoate, 2-ethyl-1-hexanol, indene, ethyl

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heptanoate, methyl octanoate, and (E,E)-α-farnesene were extracted from the salivary glands, with n-hexane released by the calling males of C. capitata. They found the chemical profiles of the released volatiles and the salivary gland suggest some of these are the pheromone components in the medfly (Gonçalves et al., 2006).

1.3.2 Infested fruit volatiles

Due to the high economic impact associated with fruit fly pests, much attentions has been paid to the development of trapping systems for detection and monitoring of insects populations (Heath et al., 1995; Thomas et al., 2008). Female fruit flies have well-developed ovipositors that insert their eggs beneath the skin of host fruits. Larvae feed and develop concealed within fruit pulp, making the infestation of fruit, difficult to detect (Kendra et al., 2007, Cheseto et al., 2018).

At entry ports worldwide, quarantine inspectors currently check incoming fruit shipments by examining a small sample of fruit for external signs of pest boring, and, if suspicious, by slicing open the fruit to search for fruit fly larvae (Hern and Dorn, 2001). Efficacy of visual inspections is questionable, especially for first instar larvae because they are clear to pale white in colour and only 2–3mm in length, which makes them difficult to detect the efficacy of visual. Gould (1995) explained that a trained agricultural inspector detected only about 35 percent of grapefruits infested with A. suspensa.

Due to this risk of pest introduction through infested fruit evading detections, there are great demands for more sensitive, high throughput screening methods for detection of fruit fly larval infestation (Li et al., 2009, Wen et al., 2019). Herbivore feeding often induces volatile emissions from fruits, and such emissions have been documented by (Karban et al., 1998; Vet, 1999). Volatile organic compounds emitted by fruits may potentially act as semi chemicals to both insects and their natural antagonists (Vet and Dicke, 1992). Most of these studies have been carried out under standard laboratory conditions and only a few deals with field situations to detect chemicals profile (Bernasconi et al., 1998; De Moraes et al., 1998). The chemical mediation of fruit fly oviposition is also known to involve volatile fruit chemicals. Phytophagous of insects assess volatile chemicals through direct physical contact and, this can identify both chemical stimulants and deterrents. This evaluation can be carried out via walking,

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palpation or drumming with others. This behaviour helps the insects discriminate suitable oviposition sites at the fruit level.

A knowledge of fruits VOCs could be used in agriculture to generate attraction or repellents to pests and resistance to pathogens in fruits (Rodríguez et al., 2013). Benelli et al. (2013) found emissions of 1-butyl esanoate, 1-butyl butylate, and 1-hexyl acetate increased in infested apples, while 1-hexyl (E)-2-methyl butenoate decreased significantly. Among apple volatiles, 2- methyl-1-butyl acetate, 1-butyl butylate, 1-hexyl acetate, 1-butyl hexanoate and 1-hexyl (E)-2- methyl butenoate, and 2-methyl-1-butyl 2-methylbutanoate elicited responses in female antennae. Kendra et al. (2011) examined grapefruits (Citrus paradisi Macfad) infested with the Caribbean fruit fly, A. suspensa (Loew) (Diptera: Tephritidae) and whether grapefruits emitted a chemical profile distinct from that of non-infested grapefruits. The results indicated that volatiles increase after oviposition; during the last instar exit stage; and in experimentally- pierced grapefruits, which were interpreted to reflect citrus peel injury. Chemicals included d- limonene and ocimene and hexyl butanoate. Boevé et al. (1996) reported that infested apples by the European apple sawfly (Hoplocampa testudinea) emitted the same compounds as healthy apples, while trans, trans-α-farnesene, trans-β-ocimene, and another terpenoid were emitted from infested fruits. Hern and Dorn (2001) reported volatile occurrences when the fruits was infested with the first instar larvae codling moth (Cydia pomonella), which is the most effective induction of volatile organic compounds, and induction with first instar larvae is generally higher than after infestation by later instars. Suckling et al. (2012) found that nine additional compounds were only detected in infested apples with brown apple moth, and these included indole, benzyl alcohol, (E)-β-ocimene, benzyl cyanide, (E)-nerolidol, and four unidentified compounds. A large amount of linalool, (Z)-3-hexenyl acetate, 4,8-dimethyl-1,3(E),7- nonatriene, germacrene, dmethyl salicylate, β-caryophyllene, (E,E)-α-farnesene, and (Z)-3- hexenyl benzoate was present in un-infested apples.

Tabilio et al. (2013) reported that 88 volatile compounds were identified from different peach cultivars infested by C. capitata. The higher amounts were butyl and 2-methylpropyl esters, hexenyl, hexyl, 3-methylbutyl; and among these, some C6 derivatives were detected, such as (Z)-3-hexenyl acetate. Hernandez et al. (1999) tested airborne volatiles produced by peaches in three stages of assay ripeness attraction by C. capitata. Several compounds have been identified

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with some increasing of concentrations of ester and benzyl alcohol. The most active compounds were ethyl benzoate, 1,2,3,4,-tetrahdronaphthalene, 4-ethyl acetophone, naphthalene and ethyl octanoate. Wang et al. (2009) reported that in the volatile composition of several peach cultivars, C6 compounds and C6 aldehydes, have been found to be prevalent.

1.4 Headspace Solid Phase Microextraction (HS-SPME)