Pollen and yeast change nectar aroma and nutritional content alone and together, but honey bee foraging reflects only the avoidance of yeast.

Floral nectar often contains pollen and microorganisms, which may change nectar's chemical composition, and in turn impact pollinator affinity. However, their individual and combined effects remain understudied. Here, we examined the impacts of the nectar specialist yeast, Metschnikowia reukaufii, and the addition of sunflower (Hellianthus annus) pollen. Pollen grains remained intact, yet still increased yeast growth and amino acid concentrations in nectar, whereas yeast depleted amino acids. Pollen, but not yeast, changed nectar sugar concentrations by converting sucrose to its monomers. Both pollen and yeast contributed emissions from nectar, though yeast volatiles were more abundant than pollen volatiles. Yeast volatile emission was positively correlated with pollen concentration and cell density, and yeast depleted a subset of pollen-derived volatiles. Honey bees avoided foraging on yeast-inoculated nectar and foraged equally among uninoculated nectars regardless of pollen content, underscoring the importance of microbial metabolites in mediating pollinator foraging.

Sampling of Volatiles in Closed Systems: A Controlled Comparison of Three Solventless Volatile Collection Methods.

Complex inter-organismal communication among plants, insects, and microbes in natural and agricultural ecological systems is typically governed by emitted and perceived semiochemicals. To understand and ultimately utilize the role of volatile semiochemicals in these interactions, headspace volatiles are routinely collected and analyzed. Numerous collection systems are available (e.g., static or dynamic; adsorption or absorption) where the choice of technique should be dependent upon the plant, insect, or microbial ecological system studied, the information sought, and the limitations of each method. Within these constraints, it remains necessary that each method detects and provides the accurate in situ, or in vitro, volatile profile of the studied system. Herein, we analyzed and compared the pros and cons of three solventless, thermal desorption systems (SPME, Tenax/cold trap, SPDE) using a synthetic standard blend of compounds mimicking a simple natural blend (benzaldehyde, b-caryophyllene, (Z)-3-hexenol, 6-methyl-5-hepten-2-one, and limonene). Direct splitless injection and Super Q collections of the standard blend were used as controls. The results indicated that related qualitative, as well as quantitative differences, could be correlated with adsorbent sampling capacity and structural bias. The results for Tenax/cold trap and SPDE also were affected by sampled headspace volumes. All solventless techniques exhibited high analytical reproducibility, with SPME and SPDE providing ease of use, low cost, and minimal instrument modifications. The more complex Tenax/cold trap technique provided higher collection efficiency. Using these results, we provide guidance for technique selection for chemical communication applications.

Zea mays Volatiles that Influence Oviposition and Feeding Behaviors of Spodoptera frugiperda.

Fall armyworm (Spodoptera frugiperda) is a major global pest of many crops, including maize (Zea mays). This insect is known to use host plant-derived volatile organic compounds to locate suitable hosts during both its adult and larval stages, yet the function of individual compounds remains mostly enigmatic. In this study, we use a combination of volatile profiling, electrophysiological assays, pair-wise choice behavioral assays, and chemical supplementation treatments to identify and assess specific compounds from maize that influence S. frugiperda host location. Our findings reveal that methyl salicylate and (E)-alpha-bergamotene are oviposition attractants for adult moths but do not impact larval behavior. While geranyl acetate can act as an oviposition attractant or repellent depending on the host volatile context and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) is an oviposition deterrent. These compounds can also be attractive to the larvae when applied to specific maize inbreds. These data show that S. frugiperda uses different plant volatile cues for host location in its adult and larval stage and that the background volatile context that specific volatiles are perceived in, alters their impact as behavioral cues.

Microbial Co-Occurrence in Floral Nectar Affects Metabolites and Attractiveness to a Generalist Pollinator.

Microbial metabolism can shape cues important for animal attraction in service-resource mutualisms. Resources are frequently colonized by microbial communities, but experimental assessment of animal-microbial interactions often focus on microbial monocultures. Such an approach likely fails to predict effects of microbial assemblages, as microbe-microbe interactions may affect in a non-additive manner microbial metabolism and resulting chemosensory cues. Here, we compared effects of microbial mono- and cocultures on growth of constituent microbes, volatile metabolite production, sugar catabolism, and effects on pollinator foraging across two nectar environments that differed in sugar concentration. Growth in co-culture decreased the abundance of the yeast Metschnikowia reukaufii, but not the bacterium Asaia astilbes. Volatile emissions differed significantly between microbial treatments and with nectar concentration, while sugar concentration was relatively similar among mono- and cocultures. Coculture volatile emission closely resembled an additive combination of monoculture volatiles. Despite differences in microbial growth and chemosensory cues, honey bee feeding did not differ between microbial monocultures and assemblages. Taken together, our results suggest that in some cases, chemical and ecological effects of microbial assemblages are largely predictable from those of component species, but caution that more work is necessary to predict under what circumstances non-additive effects are important.

Microbial metabolites elicit distinct olfactory and gustatory preferences in bumblebees.

Animals such as bumblebees use chemosensory cues to both locate and evaluate essential resources. Increasingly, it is recognized that microbes can alter the quality of foraged resources and produce metabolites that may act as foraging cues. The distinct nature of these chemosensory cues however and their use in animal foraging remain poorly understood. Here, we test the hypothesis that species of nectar-inhabiting microbes differentially influence pollinator attraction and feeding via microbial metabolites produced in nectar. We first examined the electrophysiological potential for bumblebee (Bombus impatiens) antennal olfactory neurons to respond to microbial volatile organic compounds (mVOCs), followed by an olfactory preference test. We also assessed gustatory preferences for microbial-altered nectar through both no-choice and choice feeding assays. Antennal olfactory neurons responded to some mVOCs, and bees preferred nectar solutions inoculated with the bacterium Asaia astilbes over the yeast Metschnikowia reukaufii based on volatiles alone. However, B. impatiens foragers consumed significantly more Metschnikowia-inoculated nectar, suggesting distinct roles for mVOCs and non-volatile metabolites in mediating both attraction and feeding decisions. Collectively, our results suggest that microbial metabolites have significant potential to shape interspecific, plant-pollinator signalling, with consequences for forager learning, economics and floral host reproduction.

Nectar-inhabiting microorganisms influence nectar volatile composition and attractiveness to a generalist pollinator.

The plant microbiome can influence plant phenotype in diverse ways, yet microbial contribution to plant volatile phenotype remains poorly understood. We examine the presence of fungi and bacteria in the nectar of a coflowering plant community, characterize the volatiles produced by common nectar microbes and examine their influence on pollinator preference. Nectar was sampled for the presence of nectar-inhabiting microbes. We characterized the headspace of four common fungi and bacteria in a nectar analog. We examined electrophysiological and behavioral responses of honey bees to microbial volatiles. Floral headspace samples collected in the field were surveyed for the presence of microbial volatiles. Microbes commonly inhabit floral nectar and the common species differ in volatile profiles. Honey bees detected most microbial volatiles tested and distinguished among solutions based on volatiles only. Floral headspace samples contained microbial-associated volatiles, with 2-ethyl-1-hexanol and 2-nonanone - both detected by bees - more often detected when fungi were abundant. Nectar-inhabiting microorganisms produce volatile compounds, which can differentially affect honey bee preference. The yeast Metschnikowia reukaufii produced distinctive compounds and was the most attractive of all microbes compared. The variable presence of microbes may provide volatile cues that influence plant-pollinator interactions.

In-field Volatile Analysis Employing a Hand-held Portable GC-MS: Emission Profiles Differentiate Damaged and Undamaged Yellow Starthistle Flower Heads.

INTRODUCTION: Understanding the complex chemical signalling of plants and insects is an important component of chemical ecology. Accordingly, the collection and analysis of chemical cues from plants in their natural environment is integral to elucidation of plant-insect communications. Remote plant locations and the need for a large number of replicates make in situ headspace analyses a daunting logistical challenge. A hand-held, portable GC-MS system was used to discriminate between damaged and undamaged Centaurea solstitialis (yellow starthistle) flower heads in both a potted-plant and natural setting. OBJECTIVE: To determine if a portable GC-MS system was capable of distinguishing between undamaged and mechanically damaged plant treatments, and plant environments. METHODOLOGY: A portable GC-MS utilising needle trap adsorbent technology was used to collect and analyse in situ headspace volatiles of varying yellow starthistle treatments. Principal component analysis (PCA) was used to distinguish treatments and identify biomarker volatiles. Analysis of variance (ANOVA) was used to determine differences between treatment volatile amounts. RESULTS: The portable GC-MS system detected 31 volatiles from the four treatments. Each GC-MS run was completed in less than 3 min. PCA showed four distinct clusters representing the four treatments - damaged and undamaged potted plant, and damaged and undamaged natural plant. Damage-specific volatiles were identified. CONCLUSION: The portable GC-MS system distinguished the treatments based on their detected volatile profiles. Additional statistical analysis identified five possible biomarker volatiles for the treatments, among them cyclosativene and copaene, which indicated damaged flower heads.

An overview of plant volatile metabolomics, sample treatment and reporting considerations with emphasis on mechanical damage and biological control of weeds.

INTRODUCTION: The technology for the collection and analysis of plant-emitted volatiles for understanding chemical cues of plant-plant, plant-insect or plant-microbe interactions has increased over the years. Consequently, the in situ collection, analysis and identification of volatiles are considered integral to elucidation of complex plant communications. Due to the complexity and range of emissions the conditions for consistent emission of volatiles are difficult to standardise. OBJECTIVE: To discuss: evaluation of emitted volatile metabolites as a means of screening potential target- and non-target weeds/plants for insect biological control agents; plant volatile metabolomics to analyse resultant data; importance of considering volatiles from damaged plants; and use of a database for reporting experimental conditions and results. METHOD: Recent literature relating to plant volatiles and plant volatile metabolomics are summarised to provide a basic understanding of how metabolomics can be applied to the study of plant volatiles. RESULTS: An overview of plant secondary metabolites, plant volatile metabolomics, analysis of plant volatile metabolomics data and the subsequent input into a database, the roles of plant volatiles, volatile emission as a function of treatment, and the application of plant volatile metabolomics to biological control of invasive weeds. CONCLUSION: It is recommended that in addition to a non-damaged treatment, plants be damaged prior to collecting volatiles to provide the greatest diversity of odours. For the model system provided, optimal volatile emission occurred when the leaf was punctured with a needle. Results stored in a database should include basic environmental conditions or treatments.

Leaffooted Bugs: Insect Pest Species of Growing Concern for Agriculture.

Leptoglossus (Hemiptera: Coreidae) are a diverse genus of phytophagous insects. Literature regarding Leptoglossus has increased as species are identified as emerging agricultural pests or reported outside of their native range. Within Leptoglossus, five species dominate the literature and are known pests and vectors of plant pathogenic microbes in several major crops. Despite the increasing profile of Leptoglossus, current monitoring and management methods rely primarily on visual inspection, and semiochemical tools have yet to be developed. This Perspective identifies and discusses gaps in the Leptoglossus literature as well as areas of research needed for the development of effective tools for monitoring insect populations and enabling informed pest-management practices.

Maize terpene synthase 1 impacts insect behavior via the production of monoterpene volatiles ß-myrcene and linalool.

Plant-derived volatiles are important mediators of plant-insect interactions as they can provide cues for host location and quality, or act as direct or indirect defense molecules. The volatiles produced by Zea mays (maize) include a range of terpenes, likely produced by several of the terpene synthases (TPS) present in maize. Determining the roles of specific terpene volatiles and individual TPSs in maize-insect interactions is challenging due to the promiscuous nature of TPSs in vitro and their potential for functional redundancy. In this study, we used metabolite GWAS of a sweetcorn diversity panel infested with Spodoptera frugiperda (fall armyworm) to identify genetic correlations between TPSs and individual volatiles. This analysis revealed a correlation between maize terpene synthase 1 (ZmTPS1) and emission of the monoterpene volatiles linalool and ß-myrcene. Electroantennogram assays showed gravid S. frugiperda could detect both linalool and ß-myrcene. Quantification of headspace volatiles in a maize tps1 loss-of-function mutant confirmed that ZmTPS1 is an important contributor to linalool and ß-myrcene emission in maize. Furthermore, pairwise choice assays between tps1 mutant and wild-type plants showed that ZmTPS1, and by extension its volatile products, aid host location in the chewing insect S. frugiperda, yet repel the sap-sucking pest, Rhopalosiphum maidis (corn leaf aphid). On the other hand, ZmTPS1 had no impact on indirect defense via the recruitment of the parasitoid Cotesia marginiventris. ZmTPS1 is therefore an important mediator of the interactions between maize and its insect pests.

Headspace volatiles from 52 oak species advertise induction, species identity, and evolution, but not defense.

Leaf volatiles convey information about a plant to other organisms in their proximity. Despite increasing interest in understanding the relevance of volatile emissions for particular ecological interactions, there has been relatively little effort to assess generally what information volatile profiles transmit. We surveyed the volatile profiles of wounded and unwounded leaves of 52 oak (Quercus) species. We used phylogenetic comparison and multivariate techniques to assess in what circumstances oak individuals advertised their species identity, evolutionary history, direct defenses, or damage. We found that both species identity and evolutionary history were advertised when leaves were wounded, but species could not be differentiated by odor when leaves were not wounded. Various fatty-acid derivative compounds showed the strongest phylogenetic signal suggesting that they may best disclose taxonomic affiliations in oaks. We tested whether oak volatile composition or diversity advertised high defensive investment, but we found no evidence for this. Wounded leaves disclose much about an oak species' identity and taxonomic affiliation, but unwounded leaves do not. This is consistent with the idea that volatile information is targeted toward natural enemy recruitment.

Early infestation volatile biomarkers of fruit fly Bactrocera dorsalis (Hendel) ovipositional activity in mango (Mangifera indica L.).

Infestation of agricultural commodities by insect pests results in significant economic, import and export, food safety, and invasive insect introduction issues for growers, consumers, and inspectors. The Oriental fruit fly (Bactrocera dorsalis) is considered a highly invasive insect pest with populations reported in more than 60 countries, with prevalent distributions in Asia and Africa. B. dorsalis is phytophagous with a host range encompassing hundreds of fruits and vegetables. Damage to the fruit or vegetable is inflicted through oviposition and subsequent larval feeding resulting in spoilage. Early detection of insect pest infestations is a critical component for ensuring food safety as well as controlling introduction and spread of invasive insects. However, detection of ovipositional activity and early larval development is visually difficult, thus rapid and non-destructive detection often relies on odors associated with infestation. We investigated the odors of mangoes (Mangifera indica L.) infested with B. dorsalis and compared the volatile profiles of infested mangoes to non-infested and mechanically damaged mangoes 24 h post-infestation. GC-MS and multivariate analyses provided the identification of eleven compounds unique to infested mangoes compared to mechanically damaged or non-infested fruit. Results indicated compositional and quantitative differentiation of volatile profiles among treatments for detection of infested fruit at quality checks or points of commerce.

Field evaluation of glutathione and glutamic acid as host marking pheromones for control of Tephritid fruit flies in a mango orchard in Kenya.

BACKGROUND: Tephritid fruit flies are a major constraint to the global production of horticultural crops. In Africa, an array of native and alien invasive fruit fly species represents a key challenge to the horticultural industry. In an effort to develop a safer management tool for these pests, we previously identified glutathione (GSH) and glutamic acid (GA), as the host marking pheromones (HMPs) of Ceratitis cosyra and Ceratitis rosa, respectively. Here, we report on the effectiveness of these compounds (GSH and GA) in reducing natural fruit fly population infestations in mango orchards. Mango trees at two different agroecological zones in Kenya were sprayed with HMPs, and the fruits sampled periodically and assessed for fruit fly emergence. Fruit fly emergence data were compared to two controls, the positive control using spot spraying of food bait (SS), and the negative control using water (W). RESULTS: The two HMPs and SS substantially decreased fruit fly emergence from the sampled mangoes. GSH and GA treated mangoes showed reduced C. cosyra and C. rosa infestation by ~70-75% relative to control (W), and with variation noted in the pheromone applied and the recovered fruit fly species. The adult emergence in pheromone-treated plants compared favorably with the positive control SS. However, the HMPs had little impact on reducing Bactrocera dorsalis infestation of mangoes. CONCLUSION: The decrease in fruit fly emergence in sampled mango fruits from HMP treated trees corroborate previous laboratory results and support the prospect of using HMPs in the management of African fruit fly species. © 2022 Society of Chemical Industry.

Blueberries infected with the fungal pathogen Colletotrichum fioriniae release odors that repel Drosophila suzukii.

BACKGROUND: Spotted-wing drosophila, Drosophila suzukii, is a serious pest of thin-skinned fruits. Alternative methods to control this pest are needed to reduce insecticide use, including new repellents. Previous research demonstrated that D. suzukii adults use odor cues to avoid blueberries infected with the fungal pathogen Colletotrichum fioriniae, which causes the disease anthracnose. To identify novel D. suzukii repellents, we investigated the volatile emission from experimentally-infected fruit, which were inoculated with C. fioriniae isolates in the laboratory, and from field-collected fruit, which were naturally infected and harvested from a field. We then tested the pathogen-induced volatiles on D. suzukii adult behavior. RESULTS: Volatile emission was similar between all five C. fioriniae strains, with good agreement between experimentally-infected and field-collected berries. In total, 14 volatiles were found to be more abundant in infected versus uninfected fruit headspace. In multiple-choice bioassays, nine of the 14 volatiles elicited repellency responses from adult D. suzukii. These nine volatiles were further evaluated in dual choice assays, where all nine reduced fly capture by 43-96% compared to the control. The most repellent compounds tested were the esters ethyl butanoate and ethyl (E)-but-2-enoate, which were more or equally repellent to the known D. suzukii repellents 1-octen-3-ol, geosmin, and 2-pentylfuran. Dose-response assays identified concentration-dependent effects on D. suzukii repellency and oviposition when applied individually and consistent aversion observed across doses of a 1:1 blend. CONCLUSION: We report two repellents from C. fioriniae-infected blueberries that could be useful semiochemicals for the behavioral manipulation of D. suzukii in the field. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Chemo-Ecological Insights into the Use of the Non-Host Plant Vegetable Black-Jack to Protect Two Susceptible Solanaceous Crops from Root-Knot Nematode Parasitism.

Plant parasitic nematodes (PPNs) develop through three major stages in their life cycle: hatching, infection, and reproduction. Interruption of any of these stages can affect their growth and survival. We used screenhouse pot experiments, laboratory in vitro hatching and mortality assays, and chemical analysis to test the hypothesis that the non-host Asteraceae plant vegetable black-jack (Bidens pilosa) suppresses infection of the PPN Meloidogyne incognita in two susceptible Solanaceae host plants, tomato (Solanum lycopersicum) and black nightshade (S. nigrum). In intercrop and drip pot experiments, B. pilosa significantly reduced the number of galls and egg masses in root-knot nematode (RKN)-susceptible host plants by 3-9-fold compared to controls. Chemical analysis of the most bioactive fraction from the root exudates of B. pilosa identified several classes of compounds, including vitamins, a dicarboxylic acid, amino acids, aromatic acids, and a flavonoid. In in vitro assays, the vitamins and aromatic acids elicited the highest inhibition in egg hatching, whereas ascorbic acid (vitamin) and 2-hydroxybenzoic acid (aromatic acid) elicited strong nematicidal activity against M. incognita, with LC50/48 h values of 12 and 300 ng/µL, respectively. Our results provide insights into how certain non-host plants can be used as companion crops to disrupt PPN infestation.

Detection of high levels of pyrrolizidine-N-oxides in the endangered plant Cryptantha crassipes (Terlingua Creek cat's-eye) using HPLC-ESI-MS.

INTRODUCTION: A previous investigation of pyrrolizidine alkaloids produced by nine species of Cryptantha identified at least two chemotypes within the genus. Other research has postulated that pyrrolizidine-N-oxide concentrations increase as the growing conditions become harsher, particularly with respect to water availability. Cryptantha crassipes is an endangered plant with a very limited distribution range within a dry, harsh Texan ecosystem. OBJECTIVE: To determine the pyrrolizidine alkaloid (and their N-oxides) profile and concentrations in Cryptantha crassipes. METHODOLOGY: Methanolic extracts of Cryptantha crassipes were partitioned into dilute sulphuric acid and the alkaloids concentrated using strong cation exchange, solid-phase extraction columns. Extracts were analysed using reversed-phase high-pressure liquid chromatography coupled to electrospray ionisation ion trap mass spectrometry. RESULTS: The N-oxides of lycopsamine and intermedine were the major pyrrolizidine alkaloids detected in Cryptantha crassipes. Smaller to trace amounts of other pyrrolizidine alkaloids observed were: the 7- and 3'-acetylated derivatives and the 1,2-dihydro analogs of lycopsamine-N-oxide and/or intermedine-N-oxide; a pair of unidentified N-oxides, isobaric with lycopsamine-N-oxide; and the N-oxides of leptanthine, echimiplatine, amabiline, echiumine and dihydroechiumine. Only trace amounts, if any, of the parent free base pyrrolizidine alkaloids were detected. The concentration of pyrrolizidine alkaloids was estimated to be 3-5% of the dry weight of milled leaves, or 10-50 times the levels previously reported for similar chemotypes. CONCLUSIONS: The high levels of the N-oxides of lycopsamine and intermedine establish the genus chemotype of the endangered Cryptantha crassipes and support earlier data linking high levels of N-oxides to dry, harsh growing conditions.

Survey of ex situ fruit and leaf volatiles from several Pistacia cultivars grown in California.

BACKGROUND: California is the second largest cultivator of pistachios, producing over 375 million pounds and a revenue of $787 million in 2009. Despite the agricultural and economic importance of pistachios, little is known regarding their actual volatile emissions, which are of interest owing to their potential roles as semiochemicals to insect pests. RESULTS: The ex situ volatile analysis of leaves from Pistacia atlantica, P. chinensis, P. lentiscus, P. palaestina, P. terebinthus, P. vera and P. weimannifolia demonstrated emission differences between species as well as between female and male leaves. Leaves from the female P. vera cultivars Bronte, Damghan, II, III, Kerman and Ohadi as well as fruits of P. atlantica, P. chinensis, P. lentiscus, P. palaestina, P. terebinthus and P. vera (cultivars II, III, Kaleh, Kerman, Momtaz and Ohadi) showed differences in the composition and relative quantity of major volatiles. The compounds in highest relative quantities from the various analyses were sabinene, Δ(3)-carene, ß-myrcene, α-phellandrene, limonene, (Z)-ocimene, (E)-ß-ocimene and α-terpinolene. CONCLUSION: This is the first ex situ survey of fruit and leaf volatile emissions from California-grown Pistacia species and a number of corresponding cultivars. The study provides an overview of the major and minor volatile emissions and also offers evidence of chemotypes based on monoterpenes. The results highlight the dissimilarity of major components detected between ex situ volatile collection and essential oil analysis.

Identification of Repellents from Four Non-Host Asteraceae Plants for the Root Knot Nematode, Meloidogyne incognita.

Olfactory cues guide plant parasitic nematodes (PPNs) to their host plants. We tested the hypothesis that non-host plant root volatiles repel PPNs. To achieve this, we compared the olfactory responses of infective juveniles (J2s) of the PPN Meloidogyne incognita to four non-host Asteraceae plants, namely, black-jack (Bidens pilosa), pyrethrum (Chrysanthemum cinerariifolium), marigold (Tagetes minuta), and sweet wormwood (Artemisia annua), traditionally used in sub-Saharan Africa for the management of PPNs. Chemical analysis by coupled gas chromatography-mass spectrometry (GC/MS) combined with random forest analysis, followed by behavioral assays, identified the repellents in the root volatiles of B. pilosa, T. minuta, and A. annua as (E)-ß-farnesene and 1,8-cineole, whereas camphor was attractive. In contrast, random forest analysis predicted repellents for C. cinerariifolium and A. annua as ß-patchoulene and isopropyl hexadecanoate. Our results suggested that terpenoids generally account for the repellency of non-host Asteraceae plants used in PPN management.

Volatile microbial semiochemicals and insect perception at flowers.

Many plant-associated microbial communities produce volatile signals that influence insect responses, yet the impact of floral microorganisms has received less attention than other plant microbiomes. Floral microorganisms alter plant and floral odors by adding their own emissions or modifying plant volatiles. These contextual and microbe species-specific changes in floral signaling are detectable by insects and can modify their behavior. Opportunities for future work in floral systems include identifying specific microbial semiochemicals that underlie insect behavioral responses and examining if insect species vary in their responses to microbial volatiles. Examining if documented patterns are consistent across diverse plant-microbe-insect interactions and in realistic plant-based studies will improve our understanding of how microbes mediate pollination interactions in complex system.

Essential oil yield and composition of Pistacia vera 'Kerman' fruits, peduncles and leaves grown in California.

BACKGROUND: Pistacia vera 'Kerman' is the predominant pistachio nut cultivar in the United States (California), the world's second largest producer. Despite several reports on the essential oil (EO) content in the genus Pistacia, data on 'Kerman' are limited. The EO content and volatile organic compound (VOC) emissions of tree nut orchards are of current interest to researchers investigating insect pests and the potential role of EO and VOCs as semiochemicals. To establish a basis for the VOC output of pistachios, the EO content of fruits, peduncles, and leaves was analyzed. RESULTS: Evaluated plant parts contained limonene as the primary EO component, followed by alpha-terpinolene. Peduncles were unique in containing relatively high levels of alpha-thujene. The results were reproducible between two different geographical locations. In situ solid phase microextraction (SPME) studies demonstrated the volatile emission was representative of the EO composition. CONCLUSION: This is the first report detailing the content and distribution of EO and the unique limonene-dominant profile for this Pistacia vera cultivar which may influence pistachio insect pest semiochemical research.