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Herbivore-Induced Plant Volatiles (HIPVs) are volatile signals emitted by plants to deter herbivores and attract their natural enemies. To date, it is unknown how lychee plants, Litchi chinensis, respond to the induction of leaf galls (erinea) caused by the lychee erinose mite (LEM), Aceria litchii. Aiming to reveal the role of HIPVs in this plant-mite interaction, we investigated changes in the volatile profile of lychee plants infested by LEM and their role on LEM preferences. The volatile profile of uninfested (flower buds, fruit, leaves and new leaf shoots) and infested plant tissue were characterized under different levels of LEM infestation. Volatiles were collected using head-space-solid phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analyses. Fifty-eight volatiles, including terpenoids, alcohols, aldehydes, alkanes, esters, and ketones classes were identified. Using dual-choice bioassays, we investigated the preference of LEM to uninfested plant tissues and to the six most abundant plant volatiles identified. Uninfested new leaf shoots were the most attractive plant tissues to LEM and LEM attraction or repellence to volatiles were mostly influenced by compound concentration. We discuss possible applications of our findings in agricultural settings. [ABSTRACT FROM AUTHOR]

Summary: Herbivore‐induced plant volatiles (HIPVs) are known to be perceived by neighboring plants, resulting in induction or priming of chemical defenses. There is little information on the defense responses that are triggered by these plant–plant interactions, and the phenomenon has rarely been studied in rice.Using chemical and molecular analyses in combination with insect behavioral and performance experiments, we studied how volatiles emitted by rice plants infested by the striped stemborer (SSB) Chilo suppressalis affect defenses against this pest in conspecific plants.Compared with rice plants exposed to the volatiles from uninfested plants, plants exposed to SSB‐induced volatiles showed enhanced direct and indirect resistance to SSB. When subjected to caterpillar damage, the HIPV‐exposed plants showed increased expression of jasmonic acid (JA) signaling genes, resulting in JA accumulation and higher levels of defensive proteinase inhibitors. Moreover, plants exposed to SSB‐induced volatiles emitted larger amounts of inducible volatiles and were more attractive to the parasitoid Cotesia chilonis.By unraveling the factors involved in HIPV‐mediated defense priming in rice, we reveal a key defensive role for proteinase inhibitors. These findings pave the way for novel rice management strategies to enhance the plant's resistance to one of its most devastating pests. [ABSTRACT FROM AUTHOR]

Herbivore-Induced Plant Volatiles (HIPVs) are volatile signals emitted by plants to deter herbivores and attract their natural enemies. To date, it is unknown how lychee plants, Litchi chinensis, respond to the induction of leaf galls (erinea) caused by the lychee erinose mite (LEM), Aceria litchii. Aiming to reveal the role of HIPVs in this plant-mite interaction, we investigated changes in the volatile profile of lychee plants infested by LEM and their role on LEM preferences. The volatile profile of uninfested (flower buds, fruit, leaves and new leaf shoots) and infested plant tissue were characterized under different levels of LEM infestation. Volatiles were collected using head-space-solid phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) analyses. Fifty-eight volatiles, including terpenoids, alcohols, aldehydes, alkanes, esters, and ketones classes were identified. Using dual-choice bioassays, we investigated the preference of LEM to uninfested plant tissues and to the six most abundant plant volatiles identified. Uninfested new leaf shoots were the most attractive plant tissues to LEM and LEM attraction or repellence to volatiles were mostly influenced by compound concentration. We discuss possible applications of our findings in agricultural settings.

A striking feature of plant ecology is the ability of plants to detect and respond to environmental cues such as herbivore-induced plant volatiles (HIPVs) by priming or directly activating defenses against future herbivores. However, whether seeds also respond to compounds that are common constituents of HIPV blends and initiate future plant resistance is unknown. Considering that seeds depend on other environmental cues to determine basic survival traits such as germination timing, we predicted that seeds exposed to synthetic constituents of HIPV blends would generate well-defended plants. We investigated the effect of seed exposure to common volatiles on growth, reproduction, and resistance characteristics in the model plants Arabidopsis thaliana and Medicago truncatula using herbivores from two feeding guilds. After seed scarification and vernalization, we treated seeds with one of seven different plant-derived volatile compounds for 24 h. Seeds were then germinated and the resulting plants were assayed for growth, herbivore resistance, and expression of inducible defense genes. Of all the synthetic volatiles tested, indole specifically reduced both beet armyworm growth on A. thaliana and pea aphid fecundity on M. truncatula. The induction of defense genes was not affected by seed exposure to indole in either plant species, indicating that activation of direct resistance rather than inducible resistance is the mechanism by which seed priming operates. Moreover, neither plant species showed any negative effect of seed exposure to any synthetic volatile on vegetative and reproductive growth. Rather, M. truncatula plants derived from seeds exposed to (Z)-3-hexanol and (Z)-3-hexenyl acetate grew larger compared to controls. Our results indicate that seeds are sensitive to specific volatiles in ways that enhance resistance profiles with no apparent costs in terms of growth. Seed priming by HIPVs may represent a novel ecological mechanism of plant-to-plant interactions, with broad potential applications in agriculture and seed conservation. [ABSTRACT FROM AUTHOR]

The red mite, Oligonychus yothersi (McGregor) (Acari: Tetranychidae), is a serious foliar pest of avocado (Persea americana Mill.) orchards in Chile. In summer, avocado plants release herbivore-induced plant volatiles (HIPVs) in response to feeding behaviour of O. yothersi. These HIPVs recruit natural enemies of the red mite as Parastethorus histrio (Chazeau) (Coleoptera: Coccinellidae) and Oligota pygmaea (Solier) (Coleoptera: Staphylinidae). However, P. histrio and O. pygmaea remain in infested avocado trees throughout the summer until late autumn. Therefore, we collected HIPVs, in late autumn, to test the behavioural responses of the red mite and its coleopterans predators. Volatiles were collected under semi-field conditions using the headspace technique and Porapak Q as adsorbent. The chemical analysis revealed that infested plants emitted (Z)-β-ocimene, α-farnesene, and methyl salicylate (MeSA), increasing the emissions of R-limonene. These variations triggered an attractive behaviour in P. histrio and O. pygmaea, yet O. yothersi remained indifferent. The emitted HIPVs by avocado infested plants, in late autumn, elicited tri-trophic interactions in avocado orchards, where higher R-limonene emissions and up-regulated three new volatile compounds in the volatiles profile could have influenced predator's choice, being necessary to examine. [ABSTRACT FROM AUTHOR]

Herbivore-induced plant volatiles (HIPVs) provide direct benefits to plants as antimicrobials and herbivore repellents, but their potential as direct toxins to herbivores is unclear. Here, we assayed the larvicidal activity of six common HIPVs from three different biochemical pathways and tested the hypothesis that the larvicidal activity of HIPVs is related to the host specialization of the insect pest. We first assessed β-caryophyllene, linalool, z-3-hexenyl acetate, z-3-hexenol, e-2-hexenal, and indole against the beet armyworm (Spodoptera exigua) and found that indole was sevenfold more toxic compared to the other volatiles when incorporated into the diet. Then, we tested the larvicidal activity of indole against six common, destructive pest caterpillars with varying host ranges. Consistent with our hypothesis, indole toxicity varied with caterpillar host range: indole toxicity was sevenfold higher in more specialized insect species relative to generalist insect species. That said, the LC50 of indole was comparable to other reported anti-herbivore agents even against the generalist caterpillars. Yet, indole in headspace had neither larvicidal nor ovicidal activity on any caterpillar species tested. These results support a key ecological precept of a trade-off between host specialization and chemical detoxification and also indicate that indole in particular is directly toxic to herbivores and therefore potentially useful in integrated pest management strategies. [ABSTRACT FROM AUTHOR]

Plants produce species‐specific herbivore‐induced plant volatiles (HIPVs) after damage. We tested the hypothesis that herbivore‐specific HIPVs prime neighboring plants to induce defenses specific to the priming herbivore. Since Manduca sexta (specialist) and Heliothis virescens (generalist) herbivory induced unique HIPV profiles in Nicotiana benthamiana, we used these HIPVs to prime receiver plants for defense responses to simulated herbivory (mechanical wounding and herbivore regurgitant application). Jasmonic acid (JA) accumulations and emitted volatile profiles were monitored as representative defense responses since JA is the major plant hormone involved in wound and defense signaling and HIPVs have been implicated as signals in tritrophic interactions. Herbivore species‐specific HIPVs primed neighboring plants, which produced 2 to 4 times more volatiles and JA after simulated herbivory when compared to similarly treated constitutive volatile‐exposed plants. However, HIPV‐exposed plants accumulated similar amounts of volatiles and JA independent of the combination of priming or challenging herbivore. Furthermore, volatile profiles emitted by primed plants depended only on the challenging herbivore species but not on the species‐specific HIPV profile of damaged emitter plants. This suggests that feeding by either herbivore species primed neighboring plants for increased HIPV emissions specific to the subsequently attacking herbivore and is probably controlled by JA. Both Heliothis virescens and Manduca sexta feeding induces Nicotiana benthamiana to emit species‐specific herbivore‐induced plant volatiles (HIPVs), which prime neighboring N. benthamiana plants for higher jasmonic acid and HIPVs emissions specific to the attacking herbivore independent of the priming herbivore. [ABSTRACT FROM AUTHOR]

Keywords: community dynamics; herbivore diversity; herbivore-induced plant volatiles (HIPVs); JA/SA crosstalk; multi-species attack; organismal mechanics; plant defense; sap-feeding and leaf-chewing herbivores EN community dynamics herbivore diversity herbivore-induced plant volatiles (HIPVs) JA/SA crosstalk multi-species attack organismal mechanics plant defense sap-feeding and leaf-chewing herbivores 2110 2112 3 08/19/21 20210915 NES 210915 Bridging scales of organization is one of sciences' grand challenges, and linking organismal mechanics with the dynamics of ecological communities is a case in point. Community dynamics, herbivore diversity, herbivore-induced plant volatiles (HIPVs), JA/SA crosstalk, multi-species attack, organismal mechanics, plant defense, sap-feeding and leaf-chewing herbivores I nigra i tailors its induced responses to the individual sap-feeding species, and that increased sap-feeding herbivore diversity thus results in an increase in the diversity of the defense phenotype with negative consequences for the leaf-chewing bioassay herbivore. [Extracted from the article]

Summary: Plants emit a plethora of volatile organic compounds in response to biotic and abiotic stresses. These compounds act as infochemicals for ecological communication in the phytobiome. This study reviews the role of microbe‐induced plant volatiles (MIPVs) in plant–microbe interactions. MIPVs are affected by the taxonomic position of the microbe, the identity of the plant and the type of interaction. Plants also emit exclusive blends of volatiles in response to nonhost and host interactions, as well as to beneficial microbes and necrotrophic/biotrophic pathogens. These MIPVs directly inhibit pathogen growth and indirectly promote resistance/susceptibility to subsequent plant pathogen attack. Viruses and phloem‐limiting bacteria modify plant volatiles to attract insect vectors. Susceptible plants can respond to MIPVs from resistant plants and become resistant. Recent advances in our understanding of the molecular mechanisms of MIPV synthesis in plants and how plant pathogen effectors manipulate their biosynthesis are discussed. This knowledge will help broaden our understanding of plant–microbe interactions and should facilitate the development of new emerging techniques for sustainable plant disease management. See also the Editorial by Kessler, 220: 655–658. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this review was to summarize the current information about semiochemicals with potential to be applied in insect pest management in agroecosystems. One of the great challenges to Neotropical agriculture is to reduce the indiscriminate use of pesticides, which can be minimized by using semiochemicals, a tool that can be applied in the field to manage pests and their natural enemies. In addition, small lipophilic molecules from insects and from the secondary metabolism of plants play a fundamental role in the chemical communication of different species that are present in important crops.

The giant willow aphid (Tuberolachnus salignus) is a large stem-feeding insect which forms dense colonies on infested plants. Since T. salignus is a new invasive species in New Zealand, we have a poor understanding of the plant chemical responses to aphid infestation. This study aimed to characterize the volatile organic compounds (VOCs) emissions of fifteen different willow species and hybrids growing in New Zealand, and to evaluate changes in response to T. salignus attack in a field trial. Volatiles were collected using a headspace sampling technique and analysed using gas chromatography-mass spectrometry (GC-MS). We found high variability in the volatile profiles of different species and hybrids, with (Z)-3-hexenyl acetate and (E)-β-ocimene being the only common components to all blends. Taxonomically related plants showed an overlapping pattern of VOC emission, and there seemed to be a clear separation between shrub and tree willows. Responses to aphid infestation were variable, with only four species/hybrids showing changes in their total VOC emission, or that of at least one class of VOCs. A weak positive correlation between aphid population estimates and VOC emissions suggests that responses are species-specific and not infestation-dependent. These results reveal useful information about the interaction between T. salignus and its potential host plants for biological control and pest management purposes.

In the fig–fig wasp nursery pollination system, parasitic wasps, such as gallers and parasitoids that oviposit from the exterior into the fig syconium (globular, enclosed inflorescence) are expected to use a variety of chemical cues for successful location of their hidden hosts. Behavioral assays were performed with freshly eclosed naive galler wasps. Syconia with different oviposition histories, i.e. with or without prior oviposition, were presented to wasps in no-choice assays and the time taken to the first oviposition attempt was recorded. The wasps exhibited a preference for syconia previously exposed to conspecifics for oviposition over unexposed syconia. Additionally, syconia exposed to oviposition by heterospecific wasps were also preferred for oviposition over unexposed syconia indicating that wasps recognise and respond to interspecific cues. Wasps also aggregated for oviposition on syconia previously exposed to oviposition by conspecifics. We investigated chemical cues that wasps may employ in accepting an oviposition resource by analyzing syconial volatile profiles, chemical footprints left by wasps on syconia, and syconial surface hydrocarbons. The volatile profile of a syconium is influenced by the identity of wasps developing within and may be used to identify suitable host syconia at long range whereas close range preference seems to exploit wasp footprints that alter syconium surface hydrocarbon profiles. These cues act as indicators of the oviposition history of the syconium, thereby helping wasps in their oviposition decisions. [ABSTRACT FROM AUTHOR]

Herbivore-induced plant volatiles (HIPVs) are an important cue used in herbivore location by carnivorous arthropods such as parasitoids. The effects of plant volatiles on parasitoids have been well characterised at small spatial scales, but little research has been done on their effects at larger spatial scales. The spatial matrix of volatiles ('volatile mosaic') within which parasitoids locate their hosts is dynamic and heterogeneous. It is shaped by the spatial pattern of HIPV-emitting plants, the concentration, chemical composition and breakdown of the emitted HIPV blends, and by environmental factors such as wind, turbulence and vegetation that affect transport and mixing of odour plumes. The volatile mosaic may be exploited differentially by different parasitoid species, in relation to species traits such as sensory ability to perceive volatiles and the physical ability to move towards the source. Understanding how HIPVs influence parasitoids at larger spatial scales is crucial for our understanding of tritrophic interactions and sustainable pest management in agriculture. However, there is a large gap in our knowledge on how volatiles influence the process of host location by parasitoids at the landscape scale. Future studies should bridge the gap between the chemical and behavioural ecology of tritrophic interactions and landscape ecology. [ABSTRACT FROM AUTHOR]

Crop plants exhibit a wide diversity of defensive traits and strategies to protect themselves from damage by herbivorous pests and disease. These defensive traits may be naturally occurring or artificially selected through crop breeding, including introduction via genetic engineering. While these traits can have obvious and direct impacts on herbivorous pests, many have profound effects on higher trophic levels, including the natural enemies of herbivores. Multi-trophic effects of host plant resistance have the potential to influence, both positively and negatively, biological control. Plant defense traits can influence both the numerical and functional responses of natural enemies; these interactions can be semiochemically-, plant toxin-, plant nutrient-, and/or physically-mediated. Case studies involving predators, parasitoids, and pathogens of crop pests will be presented and discussed. These diverse groups of natural enemies may respond differently to crop plant traits based on their own unique biology and the ecological niches they fill. Genetically modified crop plants that have been engineered to express transgenic products affecting herbivorous pests are an additional consideration. For the most part, transgenic plant incorporated protectant (PIP) traits are compatible with biological control due to their selective toxicity to targeted pests and relatively low non-target impacts, although transgenic crops may have indirect effects on higher trophic levels and arthropod communities mediated by lower host or prey number and/or quality. Host plant resistance and biological control are two of the key pillars of integrated pest management; their potential interactions, whether they are synergistic, complementary, or disruptive, are key in understanding and achieving sustainable and effective pest management.

Crop plants exhibit a wide diversity of defensive traits and strategies to protect themselves from damage by herbivorous pests and disease. These defensive traits may be naturally occurring or artificially selected through crop breeding, including introduction via genetic engineering. While these traits can have obvious and direct impacts on herbivorous pests, many have profound effects on higher trophic levels, including the natural enemies of herbivores. Multi-trophic effects of host plant resistance have the potential to influence, both positively and negatively, biological control. Plant defense traits can influence both the numerical and functional responses of natural enemies; these interactions can be semiochemically, plant toxin-, plant nutrient-, and/or physically mediated. Case studies involving predators, parasitoids, and pathogens of crop pests will be presented and discussed. These diverse groups of natural enemies may respond differently to crop plant traits based on their own unique biology and the ecological niches they fill. Genetically modified crop plants that have been engineered to express transgenic products affecting herbivorous pests are an additional consideration. For the most part, transgenic plant incorporated protectant (PIP) traits are compatible with biological control due to their selective toxicity to targeted pests and relatively low nontarget impacts, although transgenic crops may have indirect effects on higher trophic levels and arthropod communities mediated by lower host or prey number and/or quality. Host plant resistance and biological control are two of the key pillars of integrated pest management; their potential interactions, whether they are synergistic, complementary, or disruptive, are key in understanding and achieving sustainable and effective pest management. [ABSTRACT FROM AUTHOR]

Herbivore-induced plant volatiles ( HIPVs) mediate critical ecological functions, but no studies have quantitatively synthesized data published on HIPVs to evaluate broad patterns. We tested three hypotheses that use eco-evolutionary theory to predict volatile induction: feeding guild (chewing arthropods > sap feeders), diet breadth (specialist herbivores > generalists), and selection history (domesticated plants < wild species)., To test these hypotheses, we extracted data from 236 experiments that report volatiles produced by herbivore-damaged and undamaged plants. These data were subjected to meta-analysis, including effects on total volatiles and major biochemical classes., Overall, we found that chewers induced more volatiles than sap feeders, for both total volatiles and most volatile classes (e.g. green leaf volatiles, monoterpenes). Although specialist herbivores induced more total volatiles than generalists, this was inconsistent across chemical classes. Contrary to our expectation, domesticated species induced stronger volatile responses than wild species, even when controlling for plant taxonomy., Surprisingly, this is the first quantitative synthesis of published studies on HIPVs. Our analysis provides support for perceptions in the published literature (chewers > sap feeders), while challenging other commonly held notions (wild > crop). Despite the large number of experiments, we identified several gaps in the existing literature that should guide future investigations. [ABSTRACT FROM AUTHOR]

The citrus rootstocks sour orange and Cleopatra mandarin display differential resistance against Tetranychus urticae. Sour orange plants support reduced oviposition, growth rates and damage compared with Cleopatra mandarin plants. Jasmonic acid signalling and flavonoid accumulation have been revealed as key mechanisms for the enhanced resistance of sour orange plants., In this study, we observed that the release of T. urticae herbivore-induced plant volatiles ( HIPVs) from sour orange plants has a marked repellent effect on conspecific mites associated with the production of the terpenes α-ocimene, α-farnesene, pinene and d-limonene, and the green leaf volatile 4-hydroxy-4-methyl-2-pentanone. By contrast, T. urticae HIPVs from Cleopatra mandarin plants promote conspecific mite attraction associated with an increase in (2 -butoxyethoxy) ethanol , benzaldehyde and methyl salicylate levels., HIPVs released from sour orange plants following T. urticae infestation induce resistance in Cleopatra mandarin plants, thereby reducing oviposition rates and stimulating the oxylipin biosynthetic gene lipoxygenase2 ( LOX2). Cleopatra HIPVs do not affect the response to T. urticae of these rootstocks., We conclude that sour orange plants promote herbivore-induced resistance in Cleopatra mandarin plants and, despite the weak basal resistance of these rootstocks, herbivore resistance can be induced through the combination of HIPVs, such as α-ocimene and d-limonene. [ABSTRACT FROM AUTHOR]

Tritrophic studies involving several populations of the predatory mite Phytoseiulus longipes showed distinct life history traits depending on the prey offered and/or the plant substrate. In order to better understand the biology of this predator, the response to several combinations of prey species ( Tetranychus evansi and Tetranychus urticae), prey stages (eggs and mobile stages) and plant substrates (bean and tomato leaf discs) has been assessed for two populations of P. longipes. Unlike what was found for life history traits, both populations displayed similar behaviour: they went and stayed more on tomato than on bean, they preferred T. urticae over T. evansi and mobile stages over eggs. Combining the previous life history data with the present results suggests that P. longipes may display host-plant mediated specialization on a prey species, T. evansi. Possible underlying mechanisms are discussed, as well as directions for future work. [ABSTRACT FROM AUTHOR]

Plant defenses against herbivores include the emission of specific blends of volatiles, which enable plants to attract natural enemies of herbivores., We characterized a plastidial terpene synthase gene, Pl TPS2, from lima bean ( Phaseolus lunatus). The recombinant Pl TPS2 protein was multifunctional, producing linalool, ( E)-nerolidol and ( E, E)-geranyllinalool, precursors of ( E, E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene [ TMTT]., Transgenic Lotus japonicus and Nicotiana tabacum plants, expressing Pl TPS2 or its homolog Medicago truncatula TPS3 ( Mt TPS3), were produced and used for bioassays with herbivorous and predatory mites. Transgenic L. japonicus plants expressing PlTPS2 produced ( E, E)-geranyllinalool and TMTT, whereas wild-type plants and transgenic plants expressing MtTPS3 did not. Transgenic N. tabacum expressing PlTPS2 produced ( E, E)-geranyllinalool but not TMTT. Moreover, in olfactory assays, the generalist predatory mite Neoseiulus californicus but not the specialist Phytoseiulus persimilis was attracted to uninfested, transgenic L. japonicus plants expressing PlTPS2 over wild-type plants. The specialist P. persimilis was more strongly attracted by the transgenic plants infested with spider mites than by infested wild-type plants., Predator responses to transgenic plant volatile TMTT depend on various background volatiles endogenously produced by the transgenic plants. Therefore, the manipulation of TMTT is an ideal platform for pest control via the attraction of generalist and specialist predators in different manners. [ABSTRACT FROM AUTHOR]

In response to herbivory by cabbage white butterfly (Pieris rapae) larvae, crucifer plants emit green leaf volatiles (GLVs) that attractCotesia glomerata, a carnivorous natural enemy of the larvae. To artificially increase GLV production by crucifers, we created transgenicArabidopsisthat constitutively expressed cucumber cytosolic lipoxygenase (CsLOX2). TransgenicArabidopsis(p35S::CsLOX2.6andp35S::CsLOX2.14) infested withP. rapaelarvae were more attractive toC. glomeratathan wild type (wt) and produced more jasmonic acid.p35S::CsLOX2.14had a higher incidence of parasitism of the larvae than did wt. Infested transgenic plants emitted more (Z)-3-hexenyl acetate, (E)-β-ocimene, (Z)-β-ocimene, and DMNT than infested wt plants; (Z)-3-hexenyl acetate is known to attractCotesiawasps. Transforming cruciferous crops with cytosolicCsLOX2could aid integrated pest management via tritrophic interactions. [ABSTRACT FROM PUBLISHER]

Advances in research in the past few years on the ornamental plant torenia (Torenia spps.) have made it notable as a model plant on the frontier of genetic engineering aimed at studying ornamental characteristics and pest control in horticultural ecosystems. The remarkable advantage of torenia over other ornamental plant species is the availability of an easy and high-efficiency transformation system for it. Unfortunately, most of the current torenia research is still not very widespread, because this species has not become prominent as an alternative to other successful model plants such as Arabidopsis, snapdragon and petunia. However, nowadays, a more global view using not only a few selected models but also several additional species are required for creating innovative ornamental traits and studying horticultural ecosystems. We therefore introduce and discuss recent research on torenia, the family Scrophulariaceae, for secondary metabolite bioengineering, in which global insights into horticulture, agriculture and ecology have been advanced. Floral traits, in torenia particularly floral color, have beenextensively studied by manipulating the flavonoid biosynthetic pathways in flower organs. Plant aroma, including volatile terpenoids, has also been genetically modulated in order to understand the complicated nature of multi-trophic interactions that affect the behavior of predators and pollinators in the ecosystem. Torenia would accordingly be of great use for investigating both the variation in ornamental plants and the infochemical-mediated interactions with arthropods. [ABSTRACT FROM AUTHOR]

Plants respond to herbivory by synthesizing and releasing novel blends of volatile organic compounds (VOCs). Natural enemies are attracted to these VOCs, but little is known about the effects of these chemicals on the herbivores themselves. We studied the effect of Thaumastocoris peregrinus herbivory on VOCs released by Eucalyptus benthamii plants and the responses of this herbivore to the VOCs. In total, 12 compounds released by E. benthamii were identified. Five compounds (β-pinene, linalool, 9-epi-( E)-caryophyllene, viridiflorol, and one unidentified compound) emitted after herbivore and mechanical damage were not detected in collections from undamaged plants. The three most abundant VOCs, α-pinene, aromadendrene, and globulol, were released in greater quantities from herbivore-damaged plants compared to plants with mechanical damage, which, in turn, released greater amounts than undamaged (control) plants. The VOCs emitted after herbivore damage did not differ during the photophase and scotophase in either quantity or quality. In an olfactometer, mated female T. peregrinus showed a preference for undamaged plants over herbivore-damaged plants, and also for hexane over α-pinene at an amount equivalent to that released by a herbivore-damaged plant. In the olfactometer, virgin females did not exhibit any preference between conspecific-damaged or undamaged plants. [ABSTRACT FROM AUTHOR]

Plants produce volatile organic compounds (VOCs) in a variety of contexts that include response to abiotic and biotic stresses, attraction of pollinators and parasitoids, and repulsion of herbivores. Some of these VOCs may also exhibit diel variation in emission. In Ficus racemosa, we examined variation in VOCs released by fig syconia throughout syconium development and between day and night. Syconia are globular enclosed inflorescences that serve as developing nurseries for pollinating and parasitic fig wasps. Syconia are attacked by gallers early in their development, serviced by pollinators in mid phase, and are attractive to parasitoids in response to the development of gallers at later stages. VOC bouquets of the different development phases of the syconium were distinctive, as were their day and night VOC profiles. VOCs such as α-muurolene were characteristic of the pollen-receptive diurnal phase, and may serve to attract the diurnally-active pollinating wasps. Diel patterns of release of volatiles could not be correlated with their predicted volatility as determined by Henry's law constants at ambient temperatures. Therefore, factors other than Henry's law constant such as stomatal conductance or VOC synthesis must explain diel variation in VOC emission. A novel use of weighted gene co-expression network analysis (WGCNA) on the volatilome resulted in seven distinct modules of co-emitted VOCs that could be interpreted on the basis of syconium ecology. Some modules were characterized by the response of fig syconia to early galling by parasitic wasps and consisted largely of green leaf volatiles (GLVs). Other modules, that could be characterized by a combination of syconia response to oviposition and tissue feeding by larvae of herbivorous galler pollinators as well as of parasitized wasps, consisted largely of putative herbivore-induced plant volatiles (HIPVs). We demonstrated the usefulness of WGCNA analysis of the volatilome in making sense of the scents produced by the syconia at different stages and diel phases of their development. [ABSTRACT FROM AUTHOR]

A Headspace Solid-phase Microextraction (HS-SPME) method combined with Gas Chromatography-Mass Spectrometry (GC/MS) was developed and optimized to extrat and analyze the volatile compounds of aerial parts of Achillea collina Becker ex Rchb. and to investigate the effect of the phlem feeding aphid Myzus persicae Sulzer on the Volatile Organic Compounds (VOCs) emitted by the infested plants. The extraction of 1 g of powdered freeze dried plant samples for 120 min at 30°C using divinylbenzene-carbowax-polydimethylsiloxane (DVB/CAR/PDMS) fiber showed the highest area counts for the majority of the volatile compounds. Overall, 62 and 80 volatile compounds were detected in control and infested plant samples respectively. In A. collina infested plants, we observed a great increase in both monoterpenes and sesquiterpenes fractions. Several changes among alcohols also occurred, particularly regarding Z-3-hexen-1-ol, E-3-hexen-1-ol and E-2-hexen-1-ol proposing these compounds as herbivore-induces plant volatiles (HIPVs). New perspective for agricultural practice may derive from the opportunity to identify novel herbivores-induced plant VOCs active as plant protection agents. [ABSTRACT FROM AUTHOR]

Chemical plant strengtheners find increasing use in agriculture to enhance resistance against pathogens. In an earlier study, it was found that treatment with one such resistance elicitor, BTH (benzo-(1, 2, 3)-thiadiazole-7-carbothioic acid S-methyl ester), increases the attractiveness of maize plants to a parasitic wasp. This surprising additional benefit of treating plants with BTH prompted us to conduct a series of olfactometer tests to find out if BTH and another commercially available plant strengthener, Laminarin, increase the attractiveness of maize to three important parasitic wasps, Cotesia marginventris, Campoletis sonorensis, and Microplitis rufiventris. In each case, plants that were sprayed with the plant strengtheners and subsequently induced to release volatiles by real or mimicked attack by Spodoptera littoralis caterpillars became more attractive to the parasitoids than water treated plants. The elicitors alone or in combination with plants that were not induced by herbivory were not attractive to the wasps. Interestingly, plants treated with the plant strengtheners did not show any consistent increase in volatile emissions. On the contrary, treated plants released less herbivore-induced volatiles, most notably indole, which has been reported to interfere with parasitoid attraction. The emission of the sesquiterpenes (E)-β-caryophyllene, β-bergamotene, and (E)-β-farnesene was similarly reduced by the treatment. Expression profiles of marker genes showed that BTH and Laminarin induced several pathogenesis related (PR) genes. The results support the notion that, as yet undetectable and unidentified compounds, are of major importance for parasitoid attraction, and that these attractants may be masked by some of the major compounds in the volatile blends. This study confirms that elicitors of pathogen resistance are compatible with the biological control of insect pests and may even help to improve it. [ABSTRACT FROM AUTHOR]

Summary: •Plants under herbivore attack emit mixtures of volatiles (herbivore‐induced plant volatiles, HIPVs) that can attract predators of the herbivores. Although the composition of HIPVs should be critical for the attraction, most studies of transgenic plant‐emitted volatiles have simply addressed the effect of trans‐volatiles without embedding in other endogenous plant volatiles.•We investigated the abilities of transgenic wishbone flower plants (Torenia hybrida and Torenia fournieri) infested with spider mites, emitting a trans‐volatile ((E)‐β‐ocimene) in the presence or absence of endogenous volatiles (natural HIPVs and/or floral volatiles), to attract predatory mites (Phytoseiulus persimilis).•In both olfactory‐ and glasshouse‐based assays, P. persimilis females were attracted to natural HIPVs from infested wildtype (wt) plants of T. hybrida but not to those of T. fournieri. The trans‐volatile enhanced the ability to attract P. persimilis only when added to an active HIPV blend from the infested transgenic T. hybrida plants, in comparison with the attraction by infested wt plants. Intriguingly, floral volatiles abolished the enhanced attractive ability of T. hybrida transformants, although floral volatiles themselves did not elicit any attraction or avoidance behavior.•Predator responses to trans‐volatiles were found to depend on various background volatiles (e.g. natural HIPVs and floral volatiles) endogenously emitted by the transgenic plants. [ABSTRACT FROM AUTHOR]

Plants show a diversity of defense strategies against a wide range of herbivores. The emission of a specific blend of volatiles in response to herbivory (HIPVs - herbivore-induced plant volatiles) plays a great ecological role in indirect protection of the plants by attracting natural enemies of herbivores and priming their neighboring plants that can cause poorer foraging habitats on the 'receiver' plants. Maize plants showed induction of a blend of volatiles including monoterpenes, sesequiterpenes, homoterpenes, green leaf volatiles, and indole, in response to the specialist herbivore Mythimna separata. Conspecific plants placed downwind of infested maize plants showed reduced larval development after exposure to HIPVs, compared to those exposed to volatiles from uninfested plants. These findings indicate that exposure of maize plants to HIPVs primed these plants for enhanced defense responses to specialist herbivores of Poaceae. [ABSTRACT FROM AUTHOR]

After herbivore attack, plants release a plethora of different volatile organic compounds (VOCs), which results in odor blends that are attractive to predators and parasitoids of these herbivores. VOCs in the odor blends emitted by maize plants ( Zea mays) infested by lepidopteran larvae are well characterized. They are derived from at least three different biochemical pathways, but the relative importance of each pathway for the production of VOCs that attract parasitic wasps is unknown. Here, we studied the importance of shikimic acid derived VOCs for the attraction of females of the parasitoids Cotesia marginiventris and Microplitis rufiventris. By incubating caterpillar-infested maize plants in glyphosate, an inhibitor of the 5-enolpyruvylshikimate-3-phospate (EPSP) synthase, we obtained induced odor blends with only minute amounts of shikimic acid derived VOCs. In olfactometer bioassays, the inhibited plants were as attractive to naive C. marginiventris females as control plants that released normal amounts of shikimic acid derived VOCs, whereas naive M. rufiventris females preferred inhibited plants to control plants. By adding back synthetic indole, the quantitatively most important shikimic acid derived VOC in induced maize odors, to inhibited plants, we showed that indole had no effect on the attraction of C. marginiventris and that M. rufiventris preferred blends without synthetic indole. Exposing C. marginiventris females either to odor blends of inhibited or control plants during oviposition experiences shifted their preference in subsequent olfactometer tests in favor of the experienced odor. Further learning experiments with synthetic indole showed that C. marginiventris can learn to respond to this compound, but that this does not affect its choices between natural induced blends with or without indole. We hypothesize that for naïve wasps the attractiveness of an herbivore-induced odor blend is reduced due to masking by nonattractive compounds, and that during oviposition experiences in the presence of complex odor blends, parasitoids strongly associate some compounds, whereas others are largely ignored. [ABSTRACT FROM AUTHOR]

The giant willow aphid (Tuberolachnus salignus) is a large stem-feeding insect which forms dense colonies on infested plants. Since T. salignus is a new invasive species in New Zealand, we have a poor understanding of the plant chemical responses to aphid infestation. This study aimed to characterize the volatile organic compounds (VOCs) emissions of fifteen different willow species and hybrids growing in New Zealand, and to evaluate changes in response to T. salignus attack in a field trial. Volatiles were collected using a headspace sampling technique and analysed using gas chromatography-mass spectrometry (GC-MS). We found high variability in the volatile profiles of different species and hybrids, with (Z)-3-hexenyl acetate and (E)-β-ocimene being the only common components to all blends. Taxonomically related plants showed an overlapping pattern of VOC emission, and there seemed to be a clear separation between shrub and tree willows. Responses to aphid infestation were variable, with only four species/hybrids showing changes in their total VOC emission, or that of at least one class of VOCs. A weak positive correlation between aphid population estimates and VOC emissions suggests that responses are species-specific and not infestation-dependent. These results reveal useful information about the interaction between T. salignus and its potential host plants for biological control and pest management purposes. [ABSTRACT FROM AUTHOR]

Herbivory can induce several structural and functional alterations in the plant secretory system. Glandular trichomes are the main sites of production of volatile organic compounds (VOCs) with several chemical properties in Lamiaceae species. Ocimum species usually have three morphotypes of glandular trichomes (morphotype I is peltate and has a wide four-celled head; morphotype II is capitate and has a unicellular head; and morphotype III is capitate with a bicellular head) which produce a great amount of terpenes, although other chemical categories of substances are also produced. Despite the abundance of trichomes producing important anti-herbivory components in their leaves, the association between Ocimum species and leaf-cutter ants has been commonly registered in Brazil. We investigated the effect of leaf-cutter ant attack on the density of the glandular trichomes and on the chemistry of the VOCs released from leaves of O. gratissimum . Plants were subjected to Acromyrmex rugosus attack until 90 % of leaves were removed. After 40 days from the leaf-cutter attack, both treatments were sampled. The glandular trichome density was analysed by scanning electron microscopy. The VOCs were extracted utilizing headspace solid-phase microextraction (HS-SPME) technique and analysed by gas chromatography. Generally, the density of glandular trichomes increased in the adaxial leaf surface of the attacked plants. However, we bring novelties on this topic since we analysed the density of each morphotype separately. The morphotype I decreased in the abaxial leaf surface, and increased in the adaxial leaf surface; the morphotype II increased in both leaf surfaces; and the morphotype III decreased in the abaxial leaf surface and remained constant in the adaxial leaf surface of attacked plants. In leaves of attacked plants, the ( Z )-β-ocimene increased by 50 %, the α-selinene by 13 % and the germacrene D by 126 %, whereas the eugenol decreased by 70 %. Our data point to a differential response of each glandular morphotype in O. gratissimum and are consistent with the idea of a compartmentalization of functions among the different glandular morphotypes in the plant defence against environmental factors.

Plant defenses against herbivores include the emission of specific blends of volatiles, which enable plants to attract natural enemies of herbivores. We characterized a plastidial terpene synthase gene, PlTPS2, from lima bean (Phaseolus lunatus). The recombinant PlTPS2 protein was multifunctional, producing linalool, (E)-nerolidol and (E,E)-geranyllinalool, precursors of (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene [TMTT]. Transgenic Lotus japonicus and Nicotiana tabacum plants, expressing PlTPS2 or its homolog Medicago truncatula TPS3 (MtTPS3), were produced and used for bioassays with herbivorous and predatory mites. Transgenic L. japonicus plants expressing PlTPS2 produced (E,E)-geranyllinalool and TMTT, whereas wild-type plants and transgenic plants expressing MtTPS3 did not. Transgenic N. tabacum expressing PlTPS2 produced (E,E)-geranyllinalool but not TMTT. Moreover, in olfactory assays, the generalist predatory mite Neoseiulus californicus but not the specialist Phytoseiulus persimilis was attracted to uninfested, transgenic L. japonicus plants expressing PlTPS2 over wild-type plants. The specialist P. persimilis was more strongly attracted by the transgenic plants infested with spider mites than by infested wild-type plants. Predator responses to transgenic plant volatile TMTT depend on various background volatiles endogenously produced by the transgenic plants. Therefore, the manipulation of TMTT is an ideal platform for pest control via the attraction of generalist and specialist predators in different manners., (© 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.)