## 4 Discussion
gossypii_, our volatile analysis revealed the presence in both treatments of a characteristic blend of melon plant volatiles that has been described previously [35]; this blend is derived from five biosynthetic classes: aldehydes, alcohols, ketones, terpenoids and phenolic compounds. A number of the compounds we recorded here were found in previous publications on melon volatiles (compounds 4, 7, 9, 17 25, 32, and 39 in Table S1, Supplementary Material) [35]. Furthermore, many volatile compounds we found have been reported in a wide range of plant species and are regarded as herbivore-induced plant volatiles (compounds 4, 9, 25, and 42 in Table S1, Supplementary material) [36; 37; 38]. For example, the release of benzyl alcohol has been reported in _Camellia sinensis_ and _Coffea canephora_ under attack from different insect-feeding guilds [39] and even when mechanically damaged [40]. In aphid species, perception of some of these plant-specific volatile component assists olfactory discrimination between host and non-host plants [41]. Some of the compounds we identified were only detected in endophytically-colonized plants (compounds 8, 24, 29, 34, 38, 40, 41, 43, 46, and 47 Table S1, Supplementary Material) or were only detected in control plants and suppressed in endophytically-colonized plants (compounds 2, 3, 5, 10, 12, 13, 22, 27, 29, 35, 36, 38, 41, and 47 Table S1, Supplementary Material). These differences in production of particular VOCs could be as a result of endophytic colonization by entomopathogenic fungi. Many different alkyl benzenes have been retrieved previously from plants inoculated with entomopathogenic fungi and infested by _Delia radicum_ (Diptera: Anthomyiidae), especially in the presence of high densities of entomopathogenic fungal inoculum [42]. For example, we only detected benzyl alcohol in endophytically-colonized plants. This compound, together with methyl benzoate and benzaldehyde, are known to elicit very strong responses in the important pollininators _Manduca sexta_ and _Sphinx perelegans_ (Lepidoptera: Sphingidae) [43; 44]. Benzaldehyde, which was found in high levels in leaves that had been sprayed with isolate EABb 04/01-Tip, is thought to be a biomarker for pathogenic infections in algae, together with 1-octen-3-one and E-2-nonenal [45]. We detected the terpenoids and carotenoid derivatives, beta-ionone and trans-beta-Ionone only in endophytically-colonized plants. It is reported that carotenoid derivatives affect insect behavior [46]. For example, beta-ionone is highly attractive to beetles including _Anomala transvaalensis_ (Coleoptera: Scarabaeidae) [47]. However, this compound is repellent to _Cnaphalocrocis medialis_ (Lepidoptera: Pyralidae) [48]. Beta-ionone is also present in rice extracts and attracts rice planthoppers [49]. Another fact that is immediately apparent from this study is the great increase in alcoholic compounds released by fungal sprayed and endophytically-colonized leaves (Figure 6), although there was no difference in the quantity of aldehydes, ketones, terpenoids and phenolic compounds when they were considered as a group. In the present study, endophytic colonization of leaves by entomopathogenic fungi did not influence host plant selection by aphids, which is likely to be the case for most insect-microbe associations [26]. There have been a few studies evaluating the effect of endophytic colonization by entomopathogenic fungi on host plant selection behavior by herbivores [50; 51; 52]. In some cases, phytophagous insects are able to detect and subsequently avoid plants treated with entomopathogenic fungi [51; 52; 53] while others are attracted by plants treated with entomopathogenic fungi [50]. A major difference between these experiments and our own was the phenological stage of the plant and how long the plant had been colonized by the entomopathogenic fungi, which was longer than in our study. It might be expected that, in older plants, the volatiles emitted would be different and could change the results.