Comparative Analysis of Flower Volatiles from Nine Citrus at Three Blooming Stages

Volatiles from flowers at three blooming stages of nine citrus cultivars were analyzed by headspace-solid phase microextraction (HS-SPME)-GC-MS. Up to 110 volatiles were detected, with 42 tentatively identified from citrus flowers for the first time. Highest amounts of volatiles were present in fully opened flowers of most citrus, except for pomelos. All cultivars were characterized by a high percentage of either oxygenated monoterpenes or monoterpene hydrocarbons, and the presence of a high percentage of nitrogen containing compounds was also observed. Flower volatiles varied qualitatively and quantitatively among citrus types during blooming. Limonene was the most abundant flower volatile only in citrons; α-citral and β-citral ranked 2nd and 3rd only for Bergamot, and unopened flowers of Ponkan had a higher amount of linalool and β-pinene while much lower amount of γ-terpinene and p-cymene than Satsuma. Taking the average of all cultivars, linalool and limonene were the top two volatiles for all blooming stages; β-pinene ranked 3rd in unopened flowers, while indole ranked 3rd for half opened and fully opened flower volatiles. As flowers bloomed, methyl anthranilate increased while 2-hexenal and p-cymene decreased. In some cases, a volatile could be high in both unopened and fully opened flowers but low in half opened ones. Through multivariate analysis, the nine citrus cultivars were clustered into three groups, consistent with the three true citrus types. Furthermore, an influence of blooming stages on clustering was observed, especially with hybrids Satsuma and Huyou. Altogether, it was suggested that flower volatiles can be suitable markers for revealing the genetic relationships between citrus cultivars but the same blooming stage needs to be strictly controlled.     

Volatiles Emission Patterns in Poplar Clones Varying in Response to Ozone

The volatiles emitted from young and old leaves of two poplar clones (Populus deltoides x maximowiczii, Eridano, and P. x euramericana, I-214) were sampled after exposure to ozone (80 ppb, 5 h?d(-1), for 10 consecutive days) by solid phase microextraction and characterized by GC-MS. Only mature leaves of the ozone-sensitive Eridano clone developed necrosis in response to ozone exposure, and their membrane integrity was significantly affected by ozone (+86 and +18 % of levels of thiobarbituric acid reactive substances in mature and young leaves). The headspace of the poplar clones studied here contained mono- and sesquiterpenes, both hydrocarbons and oxygenated ones in Eridano, and only hydrocarbons in the clone I-214. Furthermore, some non-terpenes, such as C(9)-C(15) straight-chain aldehydes and C(12)-C(16) saturated and unsaturated aliphatic hydrocarbons, were detected. Other common non-terpene volatiles were oxygenated aliphatic compounds, mainly C(6)-alcohols and their acetates. Ozone exposure induced a strong change in volatile profiles, depending on clones and leaf age. Regardless of leaf age, in clone I-214, quantities of oxygenated monoterpenes tended to increase after ozone exposure, however, "O(3) x leaf age" was not significant. In clone Eridano, increases were observed in emissions of hydrocarbons and oxygenated sesquiterpenes in response to ozone treatment. (Z)-3-Hexen-1-ol and (Z)-3-hexenol acetate were present in traces in the headspace of untreated Eridano mature leaves, but quantities slightly increased after ozone treatment. Quantities of non-terpene oxygenated compounds dropped in the headspace of young leaves of both clones (-24 and -44 % in Eridano and I-214) and also in mature ones of I-214 (-50 %) after ozone exposure. Similarly, quantities of non-terpene hydrocarbons in the emissions from mature leaves of both clones (-58 and -49 %, respectively) decreased, while these compounds increased in young leaves of Eridano (+83 %). We suggest that the resistance of the poplar clone I-214 to O(3) is achieved by: i) monoterpenes constitutively present in young leaves and ii) increase of monoterpene content induced by O(3) in mature leaves.     

The Mono - and Sesquiterpene Content of Aphid-Induced Galls on Pistacia palaestina is Not a Simple Reflection of Their Composition in Intact Leaves

Pistacia palaestina Boiss. (Anacardiaceae), a sibling species of P. terebinthus also known as turpentine tree or terebinth tree, is common in the Levant region. The aphid Baizongia pistaciae L. manipulates the leaves of the plant to form large galls, which provide both food and protection for its developing offspring. We analyzed the levels and composition of mono-and sesquiterpenes in both leaves and galls of ten naturally growing trees. Our results show that monoterpene hydrocarbons are the main constituents of P. palaestina leaves and galls, but terpene levels and composition vary among trees. Despite this inter-tree variation, terpene levels and compositions in galls from different trees resemble each other more than the patterns displayed by leaves from the same trees. Generally, galls contain 10 to 60 fold higher total terpene amounts than leaves, especially of the monoterpenes α-pinene and limonene. Conversely, the leaves generally accumulate more sesquiterpenes, in particular E-caryophyllene, germacrene D and δ-cadinene, in comparison to galls. Our results clearly show that the terpene pattern in the galls is not a simple reflection of that of the leaves and suggest that aphids have a strong impact on the metabolism of their host plant, possibly for their own defense.     

Olfaction in the boll weevil,Anthonomus grandis Boh. (Coleoptera: Curculionidae): Electroantennogram studies

Electroantennogram (EAG) techniques were utilized to measure the antennal olfactory responsiveness of adult boll weevils,Anthonomus grandis Boh. (Coleoptera: Curculionidae), to 38 odorants, including both insect and host plant (Gossypium hirsutum L.) volatiles. EAGs of both sexes were indicative of at least two receptor populations: one receptor population primarily responsive to pheromone components and related compounds, the other receptor population primarily responsive to plant odors. Similar responses to male aggregation pheromone components (i.e., compounds I, II, and III + IV) were obtained from both sexes, but females were slightly more sensitive to I. Both sexes were highly responsive to components of the “green leaf volatile complex,” especially the six-carbon saturated and monounsaturated primary alcohols. Heptanal was the most active aldehyde tested. More acceptors responded to oxygenated monoterpenes than to monoterpene hydrocarbons. β-Bisabolol, the major volatile of cotton, was the most active sesquiterpene. In general, males, which are responsible for host selection and pheromone production, were more sensitive to plant odors than were females. In fact, males were as sensitive to β-bisabolol and heptanal as to aggregation pheromone components. Electrophysiological data are discussed with regard to the role of insect and host plant volatiles in host selection and aggregation behavior of the boll weevil.     

Oviposition and Electroantennogram Responses of Dioryctria abietivorella (Lepidoptera: Pyralidae) Elicited by Monoterpenes and Enantiomers from Eastern White Pine

Volatile emissions from twigs of eastern white pine, Pinus strobus L., stimulated oviposition by Dioryctria abietivorella (Grote) in laboratory bioassays. Chemical identification and percentage composition of monoterpenes emitted by twigs were determined by capillary GC and GC/MS analysis of headspace and of volatiles entrained on Porapak Q. Enantiomeric excess of optically active monoterpenes was determined by capillary GC analysis with a β-cyclodextrin chiral column. Four of the six most abundant monoterpenes identified in twig volatiles elicited a significant oviposition response. Myrcene and car-3-ene [predominantly the (+)-enantiomer] were the most active compounds in both electroantennogram (EAG) and oviposition bioassays. In contrast, (?)-limonene elicited a significant oviposition response but was the least stimulating monoterpene in EAG tests. Female EAG responses to monoterpenes generally increased with age and mating and were larger than those from males of the same age.     

Aphid and Plant Volatiles Induce Oviposition in an Aphidophagous Hoverfly

Episyrphus balteatus DeGeer (Diptera, Syrphidae) is an abundant and efficient aphid-specific predator. We tested the electroantennographic (EAG) response of this syrphid fly to the common aphid alarm pheromone, (E)-β-farnesene (EβF), and to several plant volatiles, including terpenoids (mono- and sesquiterpenes) and green leaf volatiles (C6 and C9 alcohols and aldehydes). Monoterpenes evoked significant EAG responses, whereas sesquiterpenes were inactive, except for the aphid alarm pheromone (EβF). The most pronounced antennal responses were elicited by six and nine carbon green leaf alcohols and aldehydes [i.e., (Z)-3-hexenol, (E)-2-hexenol, (E)-2-hexenal, and hexanal]. To investigate the behavioral activity of some of these EAG-active compounds, E. balteatus females were exposed to R-(+)-limonene (monoterpene), (Z)-3-hexenol (green leaf alcohol), and EβF (sesquiterpene, common aphid alarm pheromone). A single E. balteatus gravid female was exposed for 10 min to an aphid-free Vicia faba plant that was co-located with a semiochemical dispenser. Without additional semiochemical, hoverfly females were not attracted to this plant, and no oviposition was observed. The monoterpene R-(+)-limonene did not affect the females’ foraging behavior, whereas (Z)-3-hexenol and EβF increased the time of flight and acceptance of the host plant. Moreover, these two chemicals induced oviposition on aphid-free plants, suggesting that selection of the oviposition site by predatory hoverflies relies on the perception of a volatile blend composed of prey pheromone and typical plant green leaf volatiles.     

Investigation of the Anti-Melanogenic and Antioxidant Characteristics of Eucalyptus camaldulensis Flower Essential Oil and Determination of Its Chemical Composition

The effects of essential oil from Eucalyptus camaldulensis flowers oil on melanogenesis and the oil’s antioxidant characteristics were investigated. Assays of mushroom and cellular tyrosinase activities and melanin content of mouse melanoma cells were performed spectrophotometrically, and the expression of melanogenesis-related proteins was determined by Western blotting. The possible signaling pathways involved in essential oil-mediated depigmentation were also investigated using specific protein kinase inhibitors. The results revealed that E. camaldulensis flower essential oil effectively suppresses intracellular tyrosinase activity and decreases melanin amount in B16F10 mouse melanoma cells. The essential oil also exhibits antioxidant properties and effectively decreases intracellular reactive oxygen species (ROS) levels. The volatile chemical composition of the essential oil was analyzed with gas chromatography–mass spectrometry (GC/MS). The chemical constituents in the essential oil are predominately oxygenated monoterpenes (34.9%), followed by oxygenated sesquiterpenes (31.8%), monoterpene hydrocarbons (29.0%) and sesquiterpene hydrocarbons (4.3%). Our results indicated that E. camaldulensis flower essential oil inhibits melanogenesis through its antioxidant properties and by down-regulating both mitogen-activated protein kinases (MAPK) and protein kinase A (PKA) signaling pathways. The present study indicates that the essential oil has the potential to be developed into a skin care product.     

Leaf Volatiles from Nonhost Deciduous Trees: Variation by Tree Species, Season and Temperature, and Electrophysiological Activity in Ips typographus

The leaf volatiles emitted from four nonhost tree species of Ips typographus, i.e. Betula pendula, B. pubescens, Populus tremula, and Sambucus nigra, were collected outdoors by headspace sampling in situ and analyzed by GC-MS. Three major classes of compounds, aliphatics [mainly green-leaf volatiles (GLVs)], monoterpenes, and sesquiterpenes, existed in all the deciduous tree species investigated. In June, when the bark beetles are searching in flight for host trees, GLVs mainly consisting of (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol were the dominant constituents in B. pendula and S. nigra. In B. pubescens and P. tremula, sesquiterpenes (and their derivatives) and monoterpenes made up the major part of whole volatile blends, respectively. Surprisingly, sesquiterpene alcohols and other oxides released from B. pubescens in considerable amounts were not found in the closely related species, B. pendula. By August, both the total volatiles and individual compounds significantly decreased, mainly due to the maturation of leaves, since the light intensity and temperatures during sampling were the same as in June. There were almost no volatiles detected from P. tremula and S. nigra leaves in August. The total emissions from these deciduous species were significantly different among the species, with B. pubescens releasing 5–10 times more than other species. Under the conditions of constant light intensity and humidity, emissions of both total volatiles and most individual components of severed B. pendula and S. nigra branches (with fresh leaves) increased according to a saturation curve from 16°C to 40°C. Ips typographus antennae responded strongly to green leaf alcohols: (Z)-3-hexen-1-ol, 1-hexanol, and (E)-2-hexen-1-ol, but not to aldehydes or acetates in GC-EAD analyses of B. pendula and B. pubescens leaf volatiles. No antennal responses to monoterpenes, sesquiterpenes, or sesquiterpene oxides were found. These three antennally active GLVs emitted from nonhost tree leaves might be indicators of a wrong habitat in the host selection of conifer bark beetles.     

Inhibition of Nitrosomonas europaea by Monoterpenes from Coastal Redwood (Sequoia sempervirens) in Whole-Cell Studies

Inhibition by allelochemicals, including monoterpenes, has been suggested as a factor in the extremely low nitrification rates observed in coastal redwood forests. Similarities between the molecular structure of known nitrification inhibitors and some conifer monoterpenes have been suggested as one reason for the inhibition of autotrophic nitrifiers by conifer monoterpenes. The effect of monolerpenes on nitrification rate and growth of Nitrosomonas europaea was examined in whole-cell pure culture experiments using the five most abundant monoterpenes in coastal redwood needles. These are (in order of decreasing concentration in the needles) limonene, α-pinenc, sabinene, myrcene, and γ-terpinene. Four of the five compounds significantly inhibited growth of N. europaea in batch culture experiments. Short-term kinetic studies of the two most inhibitory monoterpenes, limonene and α-pinene, were performed on whole cells to evaluate the mode of interaction between these chemicals and nitrification rates. Inhibition constants (K _i) of limonene (38 μM) and α-pinene (95 μM) were determined. Lineweaver-Burk plots of nitrification in the presence of monoterpenes appear to fit a noncompetitive inhibition model; however, the mechanisms of inhibition may be more complex.     

Monoterpene Composition of Pinus sylvestris Varieties Resistant and Susceptible to Dioryctria zimmermani

The proportion of monoterpenes and enantiomeric ratios of chiral monoterpenes were determined in two susceptible and two resistant varieties of Scotch pine, Pinus sylvestris, by capillary GC analysis of headspace volatiles emitted by 9-year-old trees. Half the trees sampled in each variety had been wounded by Dioryctria zimmermani, while the other half were unwounded. The presence of wounds had no significant (P < 0.05) effect on the proportion of monoterpenes or the ratio of enantiomers of each of the optically resolved monoterpenes in the four varieties. In contrast, monoterpene composition varied significantly (P < 0.05) among varieties. However, the results do not entirely support the putative role of car-3-ene and terpinolene as an oviposition stimulant for D. zimmermani in resistant varieties of Scotch pine. Although the resistant Lake Superior Blue virtually lacked these two monoterpenes, the resistant Belgian had a relatively high concentration of car-3-ene and terpinolene. Both resistant varieties, however, emitted relatively high levels of limonene, a monoterpene associated with increased oviposition in three other Dioryctria species. There was no evidence linking enantiomeric composition of chirally resolved monoterpenes with varietal resistance. The relative importance of monoterpenes as resistance factors and oviposition stimulants is discussed.     

Attraction of adult sweet potato weevils,Cylas formicarius elegantulus (Summers), (Coleoptera: Curculionidae), to sweet potato leaf and root volatiles

A dual-choice olfactometer was developed to study the responses of sweet potato weevils,Cylas formicarius elegantulus (Summers), to volatiles from the sweet potato,Ipomoea batatas (L.) Lam. Both males and females were attracted by volatiles from sweet potato leaves and a methylene chloride leaf extract. Females, but not males, responded to volatiles from storage roots and a methylene chloride root extract. Leaves and storage roots from four sweet potato cultivars (Centennial, Jewel, Resisto, and Regal) were attractive to female weevils; however, the attractant response varied with cultivar. GC profiles from leaf and root extracts, and GC-MS analysis of leaf extract, for Jewel cultivar enabled the volatile peaks to be identified as sesquiterpenes.     

Changes in leaf mono- and sesquiterpene metabolism with nitrate availability and leaf age inHeterotheca subaxillaris

The concentration of leaf mono- and sesquiterpenes is greater in nitrate-limited than in nitrate-richHeterotheca subaxillaris plants and is highest in young leaves and declines with leaf age. To determine whether rates of volatile terpene synthesis and/or loss vary with nitrate availability and leaf age, incorporation of¹⁴C from photosynthetically fixed¹⁴CO₂ and the subsequent loss of label was measured in plants grown under nitrate-limited and nitrate-rich conditions.¹⁴C incorporation into mono- and sesquiterpenes was greater in nitrate-limited than in nitrate-rich plants and was highest in young leaves and declined with leaf age. Incorporation continued for several days after exposure, while loss of label was slow until leaves were 4–6 weeks old. These results suggest that the higher leaf volatile terpene content observed under nitrate limitation apparently results from increased synthesis per leaf and accumulation of mono- and sesquiterpenes in immature leaves of nitratepoor plants. Furthermore, volatile terpene synthesis is highest in young leaves, declines with leaf age, and is very low in older leaves. Carbon used for synthesis of this pool may be derived from both current photosynthesis as well as carbon transported to young leaves from older leaves. These data are consistent with hypotheses that predict that greater levels of carbon-based chemical defenses occur in plants under nutrient limitation. The apparent low metabolic cost of maintenance (i.e., slow turnover) of the accumulated terpenoid pool would limit the energetic cost of volatile terpenes as a chemical defense.     

Engelmann Spruce Chemotypes in Colorado and their Effects on Symbiotic Fungi Associated with the North American Spruce Beetle

Conifer secondary metabolites play a key role in mechanisms of resistance to biotic disturbance, especially by bark beetles and beetle-associated microorganisms. Here, we describe variation in constitutive monoterpenes isolated from Engelmann spruce, Picea engelmannii, phloem across fourteen high-elevation populations in the Rocky Mountains of Colorado, and test interactions between phloem monoterpenes and an endophloedic symbiotic fungus, Leptographium abietinum, associated with the North American spruce beetle, Dendroctonus rufipennis. We consistently identified ten monoterpenes in Engelmann spruce phloem, and the trees in our samples could be classified into two geographically interspersed chemical phenotypes, or ‘chemotypes’: one in which α- and β-pinene were the most abundant monoterpenes, and one in which 3-carene was the most abundant monoterpene. Media amended with low concentrations of α-pinene, β-pinene, 3-carene, myrcene, and terpinolene stimulated growth of L. abietinum. Increasing monoterpene concentrations uniformly retarded fungal growth. Linalool completely suppressed fungal growth at all concentrations, while terpinolene completely suppressed growth at low and intermediate concentrations, indicating relatively high toxicity of these compounds. Tests with monoterpene blends representing the ‘average’ monoterpene composition of each chemotype indicated that representative chemotypes are equivalent in fungistatic activity, with chemotype blends being inhibitory even at low concentrations. Total constitutive monoterpene abundances in Engelmann spruce phloem ranged from 42 to 1796 μg/g. Induction of Engelmann spruce phloem monoterpenes in response to L. abietinum or other biotic agents has yet to be quantified, but is important for further understanding Engelmann spruce resistance to the D. rufipennis-L. abietinum complex.     

Electroantennogram responses ofTrirhabda bacharides (weber) (Coleoptera: Chrysomelidae) to plant volatiles

Electroantennograms (EAGs) were recorded fromTrirhabda bacharides Le Conte (Coleoptera: Chrysomelidae) females to 28 odorants and volatiles emanating from leaves of 26 plant species including three known host plants,Baccharis halimifolia L.,B. neglecta Britt, andB. salicina T. & G. (Compositae: Asterae). Antennal receptors were highly responsive to components of the green leaf volatile complex, especially 6-carbon saturated and monounsaturated alcohols andtrans-2-hexenal. EAGs elicited by heptanal were greater than those elicited by any other saturated aldehyde. Oxygenated monoterpenes were more active than monoterpene hydrocarbons. -Bisabolol was the most active sesquiterpene. In general, EAGs to volatiles emanating fromBaccharis and other composite species were greater than those elicited by species from other families. Furthermore, when one considers only plants occurring in the environs ofT bacharides hostB. neglecta, EAGs elicited by its host plant were at least two times greater than those elicited by other coinhabiting plants.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.     

Volatiles from Psylla-Infested Pear Trees and Their Possible Involvement in Attraction of Anthocorid Predators

Previous work showed that anthocorid predators aggregate around gauze cages containing Psylla-infested trees in a pear orchard. Because anthocorids responded to odor from Psylla-infested leaves in a laboratory test, it was hypothesized that these aggregative responses in the field were triggered by olfaction of compounds associated with Psylla injury. We present chemical analyses of volatiles from damaged and undamaged plants and studies on behavioral responses of anthocorid predators to compounds released by damaged plants. Leaf headspace volatiles from clean and Psylla-infested pear trees were collected on Tenax and identified by GC-MS after thermodesorption. Twelve volatiles were found exclusively in headspace samples from Psylla-infested leaves. Six were present in significantly higher quantities in samples from infested leaves: the monoterpene, (E,E)-α-farnesene, the phenolic, methyl salicylate, and the green leaf compounds, (Z)-3-hexen-1-yl acetate, (Z)-3-hexen-1-ol, 1-hexyl-acetate, and 1-penten-3-ol. These compounds are known to be produced by plants, and damage by pear psyllids seems to trigger their emission. Blend composition varied and was partly correlated with tree or leaf age and degree of Psylla infestation. To study whether compounds associated with leaf injury elicit olfactory responses in anthocorid predators, apple-extracted (E,E)-α-farnesene, synthetic methyl salicylate, and (Z)-3-hexen-1-yl acetate were offered in a Y-tube olfactometer to field-collected adult Anthocoris spp. Significant positive responses were found to both the monoterpene and the phenolic, but not to the green leaf volatile. The results lend support to the hypothesis that predator attraction to herbivore-infested pear trees is mediated by herbivory-induced plant volatiles.     

Volatile, Potential Attractants from Ripe Coffee Fruit for Female Mediterranean Fruit Fly

Twenty-eight volatile compounds from freshly crushed, ripe, dark red coffee fruit, Coffea arabica, were identified by dynamic headspace analysis techniques. Identifications were made on the basis of a comparison of Kovats indices and GC-MS spectra for unknowns and authentic samples. Of the compounds identified, 10 were alcohols, nine were aldehydes, five were ketones, and four were monoterpenes. The five most abundant volatiles in decreasing order were hexanal (21%), 2-(E)-hexenal (11%), 3-methyl-1-butanol (9.0%), 3-methyl-1-butanal (8.5%), and 1-hexanol (8.4%). The five least abundant volatiles of the 28 identified, in increasing order, were decanal (0.19%), methyl hexanoate (0.33%), pulegone (0.44%), α-isomenthone (0.45%), and 2-nonanone (0.55%). In preliminary tests, many of the identified volatiles attracted more female Mediterranean fruit flies than the control.     

Volatiles released from individual spruce bark beetle entrance holes Quantitative variations during the first week of attack

Volatiles released from individual entrance holes of eight spruce bark beetles (Ips typographus) were collected during the first week of attack on a resistant host tree. In order to quantify the release of the highly volatile 2-methyl-3-buten-2-ol (MB) from attacking males, a new method was developed with deuterated quantification standard released at the time of collection. The amounts of collected volatiles, as analyzed by GC and GC-MS, showed a large variation between individual holes and also between subsequent entrainments from the same hole. Most of the quantified compounds on the average have two maxima, with a pronounced intervening depression. The amounts of releasedcis-verbenol (cV) increased five times during the first two days, while the amounts of MB were consistently high. The attacked spruce tree was not taken by the beetles, and the average amounts of the two aggregation pheromone components, MB and cV, increased again after the first maxima. The first peak of oxygenated monoterpene, released in the beginning of the attack containing -terpineol, terpinen-4-ol, bornyl acetate,trans-pinocarveol, and verbenone, was possibly due to spontaneous oxidation of monoterpene hydrocarbons from the tree. Microorganisms established in the gallery wall phloem probably participated in the production of oxygenated monoterpenes during the second increase.Ips typographus (Coleoptera: Scolytidae).     

Attraction and Oviposition of <Emphasis Type="Italic">Tuta absoluta</Emphasis> Females in Response to Tomato Leaf Volatiles

The tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae) is a devastating pest of cultivated tomato Solanum lycopersicum throughout South and Central America and Europe. We aimed to characterize the behavioral mechanisms and the chemical cues involved in host selection of T. absoluta females by chemical analysis of tomato leaf volatiles, wind tunnel attraction assays, and oviposition bioassays. Tomato leaf odor elicited in mated females upwind orientation flight followed by landing as well as egg-laying, demonstrating the essential role of plant volatiles in T. absoluta host-finding behavior. In wind tunnel and oviposition choice experiments, T. absoluta females significantly preferred tomato S. lycopersicum over wild tomato Solanum habrochaites, which is resistant to larval feeding. This indicates that leaf volatiles provide information on the suitability of plants as larval hosts. Mated females also discriminated three cultivars of S. lycopersicum according to their volatile profiles. Headspace collections from leaves of these three cultivars contained large amounts of β-phellandrene, followed by limonene, 2-carene, and (E)-β-caryophyllene, which together accounted for more than 70% of tomato foliage headspace. Most leaf volatiles were released by all three cultivars, but they showed significant differences with respect to the presence of a few minor compounds and blend proportion. This is an initial study of the volatile signatures that mediate attraction and oviposition of tomato leafminer T. absoluta in response to its main host, tomato.     

Systemically Induced Plant Volatiles Emitted at the Time of “Danger”

Feeding by Pieris brassicae caterpillars on the lower leaves of Brussels sprouts (Brassica oleracea var. gemmifera) plants triggers the release of volatiles from upper leaves. The volatiles are attractive for a natural antagonist of the herbivore, the parasitoid Cotesia glomerata. Parasitoids are attracted only if additional damage is inflicted on the systemically induced upper leaves and only after at least three days of herbivore feeding on the lower leaves. Upon termination of caterpillar feeding, the systemic signal is emitted for a maximum of one more day. Systemic induction did not occur at low levels of herbivore infestation. Systemically induced leaves emitted green leaf volatiles, cyclic monoterpenoids, and sesquiterpenes. GC-MS profiles of systemically induced and herbivore-infested leaves did not differ for most compounds, although herbivore infested plants did emit higher amounts of green leaf volatiles. Emission of systemically induced volatiles in Brussels sprouts might function as an induced defense that is activated only when needed, i.e., at the time of caterpillar attack. This way, plants may adopt a flexible management of inducible defensive resources to minimize costs of defense and to maximize fitness in response to unpredictable herbivore attack.     

Yellow-Cedar, <Emphasis Type="Italic">Callitropsis</Emphasis> (<Emphasis Type="Italic">Chamaecyparis</Emphasis>) <Emphasis Type="Italic">nootkatensis</Emphasis>, Secondary Metabolites,Biological Activities,and Chemical Ecology

Yellow-cedar, Callitropsis nootkatensis, is prevalent in coastal forests of southeast Alaska, western Canada, and inland forests along the Cascades to northern California, USA. These trees have few microbial or animal pests, attributable in part to the distinct groups of biologically active secondary metabolites their tissues store for chemical defense. Here we summarize the new yellow-cedar compounds identified and their biological activities, plus new or expanded activities for tissues, extracts, essential oils and previously known compounds since the last review more than 40 years ago. Monoterpene hydrocarbons are the most abundant compounds in foliage, while heartwood contains substantial quantities of oxygenated monoterpenes and oxygenated sesquiterpenes, with one or more tropolones. Diterpenes occur in foliage and bark, whereas condensed tannins have been isolated from inner bark. Biological activities expressed by one or more compounds in these groups include fungicide, bactericide, sporicide, acaricide, insecticide, general cytotoxicity, antioxidant and human anticancer. The diversity of organisms impacted by whole tissues, essential oils, extracts, or individual compounds now encompasses ticks, fleas, termites, ants, mosquitoes, bacteria, a water mold, fungi and browsing animals. Nootkatone, is a heartwood component with sufficient activity against arthropods to warrant research focused toward potential development as a commercial repellent and biopesticide for ticks, mosquitoes and possibly other arthropods that vector human and animal pathogens.