Journal of Chemical Ecology

In classic coevolutionary interactions, host plants are thought to accrue novel chemical defenses which are later countered by detoxification strategies and sometimes sequestration in specialist herbivores. We recently discovered that unusual nitrogen- and sulfur-containing (N,S-) cardenolides in some milkweed species are highly toxic, and broken down to less toxic forms which are sequestered by monarch butterflies (Danaus plexippus). Here we isolated and purified five dominant cardenolide toxins from the tropical milkweed, Asclepias curassavica, a globally abundant host plant of monarchs, and fed them to caterpillars individually or in mixture. We hypothesized that the two N,S-cardenolides in A. curassavica (uscharin and voruscharin) would reduce caterpillar growth and sequestration more than other abundant related cardenolides (15-Hydroxy calotropin, frugoside, calactin). Overall, cardenolide treatments caused monarchs to feed more and grow more compared to controls; nonetheless, one N,S-cardenolide (voruscharin) was not stimulatory and caused substantial reductions in growth efficiency. Consuming N,S-cardenolides caused caterpillars to sequester the lowest total amounts of cardenolides, and also reduced their efficiency of sequestration. We next tested the phytochemical diversity hypothesis, that toxin mixtures pose a substantial burden for caterpillars compared to individual compounds provided in equimolar concentrations. We prepared two types of mixtures, one containing equal concentrations of the five compounds and another "realistic mixture" where toxin concentrations reflect their natural proportions in leaves. Mixtures had a negative impact on caterpillar feeding, growth, sequestration, and sequestration efficiency compared to the average of single compounds. The equal and realistic mixtures had similar impacts on feeding and growth, but feeding on the realistic mixture resulted in the lowest sequestration. We conclude that as a result of coevolutionary interactions, even sequestering herbivores may be thwarted by highly specialized plant metabolites such as N,S-cardenolides, and that phytochemical mixtures strengthen plant defense. Toxin mixtures likely challenge detoxification and transport of plant defenses, reducing the herbivores growth and sequestration.

Plants exposed to volatile signals from herbivore-infested neighbors can activate faster and stronger defenses against subsequent herbivore attack, a phenomenon called defense priming. However, the specific volatile components responsible for activating defense priming remain unclear. Here, we examined the role of green leaf volatiles (GLV) by silencing their biosynthesis using virus-induced gene silencing technique. Exposure to full blend of herbivore-induced plant volatiles (HIPV) primed receiver plants for enhanced production of all 5 groups of HIPV (GLV, monoterpenes, sesquiterpenes, aldoximes, and indole). When GLV production was silenced in emitter plants, receiver plants were no longer primed for terpene production. However, exposure to (Z)-3-hexenol (Z3HOL) alone primed receiver plants for terpene production. These results suggest that GLV are necessary, and Z3HOL alone is sufficient, to prime terpene production in receiver plants. Consistent with enhanced resistance, Manduca sexta larvae feeding on Z3HOL-or HIPV-primed plants consumed less leaf tissue and exhibited reduced growth compared with controls. Importantly, priming did not impose fitness costs, as Z3HOL-exposed plants showed normal growth but produced more seed capsules and seeds than control plants. Together, these findings suggest that Z3HOL alone is sufficient to prime plants for better defense without compromising their ability to grow and reproduce.

Insect herbivores such as caterpillars, are under strong selection pressure from natural enemies, especially parasitoid wasps. Although the role of olfaction in host-plant seeking has been investigated in great detail in parasitoids and adult lepidopterans, the caterpillar olfactory system and its significance in tri-trophic interactions remain poorly understood. In this study, we investigated the olfactory system of Pieris brassicae caterpillars and the importance of olfactory information in the interactions among this herbivore, its host plant Brassica oleracea and its primary natural enemy Cotesia glomerata. To examine the role of olfaction, we utilized CRISPR/Cas9 to knockout the odorant receptor co-receptor (Orco). This knockout (KO) impaired olfactory detection and primary processing in the brain. Orco KO caterpillars exhibited reduced weight and lost preference for their optimal food plants. Interestingly, the KO caterpillars also experienced reduced weight when challenged by the parasitoid C. glomerata whose ovipositor had been removed, and the mortality of the KO caterpillars under the attack of unmanipulated parasitoids increased. We then investigated the behavior of P. brassicae caterpillars in response to volatiles from plants attacked by conspecific caterpillars and volatiles from plants on which the caterpillars were themselves attacked by C. glomerata. After analyzing the volatile compounds involved in these interactions, we concluded that olfactory information enables caterpillars to locate suitable food sources more efficiently as well as to select enemy-free spaces. Our results reveal the crucial role of olfaction in caterpillar feeding and natural-enemy avoidance, highlighting the significance of chemoreceptor genes in shaping ecological interactions.

The fall armyworm (FAW, Spodoptera frugiperda) is a well-known crop pest that feeds mainly on grasses. Separate strains are known to infest maize (corn) and rice that show varying degrees of developmental and metabolic differences, as well as reproductive isolation. Here we show that the greater performance of the corn compared to the rice strain on maize leaves may be explained by several factors. Maize plants respond to herbivory by the rice strain with greater levels of defense hormone signaling and greater accumulation of defensive benzoxazinoids. Moreover, measurements of the activity of a glucosyltransferase involved in benzoxazinoid metabolism and the transcript levels of the encoding gene revealed that the corn strain had higher benzoxazinoid detoxification potential than the rice strain. The two strains also exhibit constitutive differences in the expression of an alternate variant, with potential consequences for differential regulation of the glucosylation activity. These factors may account for the better performance of corn strain larvae on maize leaves, perhaps in combination with the other differences we found in maize defense metabolites after FAW herbivory by untargeted metabolomics.

Application of sex pheromone is the most environmental-friendly technique to control pests. Moreover, it has been discovered that pheromone analogs can disturb or inhibit mating communication in some species of moths. Ectropis grisescens Warren (Lepidoptera: Geometridae), is the most severe tea defoliator in China. Thus, in our study, an analog of the pest sex pheromone component, (Z, Z, Z)-3,6,9-nonadecadiene (Z3Z6Z9-19:Hy), was selected to determine its potential activity in controlling the pest. Electroantennogram (EAG), Y-tube olfactometer, and wind tunnel experiments separately showed potential inhibition of Z3Z6Z9-19:Hy. The response elicited by Z3Z6Z9-19:Hy displayed a dose-dependent way in EAG test. Furthermore, in Y-tube olfactometer, percentage of positive response of E. grisescens males was significantly (P<0.01) reduced by Z3Z6Z9-19:Hy up to 70%. In wind tunnel, all types of behavioral response were significantly (P<0.01) inhibited by Z3Z6Z9-19:Hy, percentage of contacting source was utterly inhibited at the lowest dose tested. Based on these results, the combination of the analog and SNMP1 protein was also studied. Our study revealed the potential of Z3Z6Z9-19:Hy as a sex pheromone inhibitor, which would provide new perspectives in monitoring and mating disruption of E. grisescens in pest-control strategies.

Once emitted, semiochemicals are exposed to reactive environmental factors that may alter them, thus disrupting chemical communication. Some species, however, might have adapted to detect environmentally mediated breakdown products of their natural chemicals as semiochemicals. We demonstrate that air, water vapor, and ultraviolet (UV) radiation break down unsaturated cuticular hydrocarbons (CHCs) of Periplaneta americana (American cockroach), resulting in the emission of volatile organic compounds (VOCs). In behavioral assays, nymphs strongly avoided aggregating in shelters exposed to the breakdown VOCs from cuticular alkenes. The three treatments (air, water vapor, UV) produced the same VOCs, but at different time-courses and ratios. Fourteen VOCs from UV-exposed CHCs elicited electrophysiological responses in nymph antennae; 10 were identified as 1-pentanol, 1-octanol, 1-nonanol, tetradecanal, acetic acid, propanoic acid, butanoic acid, pentanoic acid and hexanoic acid. When short-chain fatty acids were tested as a mix and a blend of the alcohols and aldehyde was tested as a second mix, nymphs exhibited no preference for control or treated shelters. However, nymphs avoided shelters that were exposed to VOCs from the complete 10-compound mix. Conditioned shelters (occupied by cockroaches with feces and CHCs deposited on the shelters), which are normally highly attractive to nymphs, were also avoided after UV-exposure, confirming that breakdown products from deposited metabolites, including CHCs, mediate this behavior. Our results demonstrate that common environmental and anthropogenic agents degrade CHCs into volatile semiochemicals that may serve as necromones or epideictic pheromones, mediating group formation and dissolution.\n\nSignificance StatementCuticular hydrocarbons (CHCs) cover the outer surface of insects, where they prevent water loss and serve as sex pheromones and in nest-mate recognition in social insects. Although CHCs are not volatile, they can be broken into volatile fragments by reacting with environmental agents. We demonstrate that volatile breakdown products of CHCs affect the social behavior of the American cockroach. A synthetic mix of volatiles dispersed cockroaches away from shelters, signaling an unsuitable shelter. These results highlight that some insect species have evolved communication strategies that exploit environmental and anthropogenic agents to produce bioactive compounds that mediate ecological interactions.

Outbreaks of the Eurasian spruce bark beetle (Ips typographus) have decimated millions of hectares of conifer forests in Europe in recent years. The ability of these 3-6 mm long insects to kill mature trees over a short period has been ascribed to two main factors: (1) mass attacks on the host tree to overcome tree defenses and (2) the presence of fungal symbionts that support successful beetle development in the tree. While the role of pheromones in coordinating mass attacks has been well studied, the role of chemical communication in maintaining the fungal symbiosis is poorly understood. We previously demonstrated that I. typographus can recognize beneficial fungal symbionts of the genera Grosmannia, Endoconidiophora and Ophiostoma by their de novo synthesized volatile compounds. Here, we hypothesize that the fungal symbionts of the bark beetles might metabolize spruce resin monoterpenes of the beetles host tree, Norway spruce (Picea abies), and that the volatile products could be used as cues by beetles for locating breeding sites with beneficial symbionts. We show that Grosmannia penicillata and other fungal symbionts altered the profile of spruce bark volatiles by converting the major monoterpenes into an attractive blend of oxygenated derivatives. Bornyl acetate was metabolized to camphor, and - and {beta}-pinene to trans-4-thujanol and other oxygenated products. Other co-occurring non-beneficial fungi (Trichoderma sp.) also produce oxygenated monoterpenes, but in non-attractive ratios. Extensive electrophysiological measurements showed that the bark beetle possesses dedicated olfactory sensory neurons for oxygenated metabolites. Compounds such as camphor and trans-4-thujanol attracted beetles at specific doses in olfactory experiments, and the presence of symbiotic fungi enhanced attraction of females to pheromones. Finally, we show that colonization of fungal symbionts on spruce bark diet stimulated beetles to make tunnels into the diet. Collectively, our study suggests that the blends of oxygenated metabolites of conifer monoterpenes produced by fungal symbionts are used by bark beetles as attractive cues to find breeding or feeding sites containing their essential microbial symbionts. The oxygenated metabolites may aid beetles in assessing the presence of the fungus, the defense status of the host tree and the density of conspecifics at potential feeding and breeding sites.

Hostplant location and conspecific aggregation on the hostplant are the key behaviors of several herbivore insect species. The cues used by insects for host identification and aggregation initiation have been researched mainly using a single hostplant species. The chemical repertoire of plants, including volatile and non-volatile secondary metabolites, is critical in mediating these processes. In natural ecosystems, often several closely related plant species co-occur. Despite these related plant species similar chemical repertoires, insects proficiently locate their hosts. How they resolve such complex chemical cues is understudied. To study the basis of such resolution, we used five commonly co-occurring Ipomoea spp. as hostplants and four Chiridopsis spp. (beetles) as their herbivores. In this wild sympatric system from the Western Ghats of India, monophagous, biphagous, and oligophagous Chiridopsis spp. are specialist herbivores of different Ipomoea species. We studied the chemistry of these beetles stringent host-specificity by determining the roles of chemical cues in hostplant location and aggregation. We analyzed beetles hostplant preferences vis-a-vis hostplant volatile blends. We found plant volatiles as the primary hostplant identification cues. Using GC-MS/-FID and SPME headspace analyses, we characterized odor blends of the five Ipomoea spp. and identified putative attractants and repellents for each Chiridopsis sp. using multivariate statistics. We determined their attractant or deterrent natures using behavioral assays and ascertained their perception by the antennal olfactory receptors using electroantennography. Beetles responded to these compounds only when they were delivered via their hostplant odor blends. Beetles did not respond when these compounds were given singularly or via non-host odor blends. We infer that these semiochemicals attractant, repellent, or neutral characters are associated with the hostplants volatile blend-the matrix. We integrated the multi-source data to visualize this in-flight odor perception by representing odor as color variations or odor images. Odor imaging revealed beetles differential olfactory perception of different hostplants and indicated how a beetle distinguishes between two closely-related plant species. Additionally, it showed a different olfactory perception of the same hostplant by different closely-related beetle species, suggesting they have evolved to recognize the same odor using different components. Our work demonstrates that the hostplants odor blend matrix is crucial; beetles do not respond to attractants/ repellents without it. Together, the closely-related plant species form an ideal system to understand how insects perceive subtle differences between hosts and non-host cues in nature. This investigation also underlines the relevance of studying entire odor blends over individual compounds.

Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae) is one of the most important insect pests that attack the rice crop, Oryza sativa L., in China, feeding on rice leaves. Chilo suppressalis and Sesamia inferens are two common insects living within the same ecological system that feed on rice stalks. Their behavior could affect C. medinaliss choice of oviposition place, so we tested the electroantennogram (EAG) response of C. medinalis to a conspecific sex pheromone (Z11-18:OH; Z11-18:Ald; Z13-18:OH; Z13-18:Ald) and two other insects pheromone compounds (Z9-16:Ald; Z11-16Ald; Z11-16:OH;Z11-16:Ac and 16:Ald). The results indicate C. medinalis can detect those pheromones and is sensitive to Z11-16:Ald and Z9-16:Ald. In the heterologous expression system of Xenopus oocytes, we cloned three pheromone receptor genes, CmedPR1, CmedPR2, and CmedPR3. These had the same electroantennogram response, in addition to the response to the conspecific pheromone. CmedPR2 and CmedPR3 displayed strong sensitivity to Z11-16Ald and Z9-16:Ald. These results may contribute to clarifying how C. medinalis recognizes pheromones and interspecies communication.

The Asian Citrus Psyllid (ACP), Diaphorina citri, severely threatens citrus production worldwide by transmitting the greening(= Huanglongbing)-causing bacterium Candidatus Liberibacter asiaticus. There is growing evidence that the push-pull strategy is suitable to partially mitigate HLB by repelling ACP with transgenic plants engineered to produce repellents and attracting the vector to plants with a minimal disease transmission rate. Species that pull ACP away from commercial citrus plants have been identified, and transgenic plants that repel ACP have been developed. The concept of a repellent-producing plant was first demonstrated with an Arabidopsis line engineered to overexpress a gene controlling the synthesis of {beta}-caryophyllene and other sesquiterpenes. We have analyzed the volatile organic compounds released by this Arabidopsis line and identified -humulene, -copaene, and trace amounts of {beta}-elemene, in addition to {beta}-caryophyllene. Behavioral measurements demonstrated that -copaene repels ACP at doses ca. 100x lower than those needed for {beta}-caryophyllene repellence. In contrast, -humulene is innocuous at the level emitted by the transgenic plant. We confirmed that a mixture of the three sesquiterpenes in the ratio 100:10:1 repels ACP. Likewise, a commercial sample of refined copaiba oil containing the three sesquiterpenes, in a proportion similar to that in the transgenic plant, repelled ACP.

Insect sex pheromones are important chemical signals in sexual communication, they are traditionally thought to be inactive to larvae. However, it was found that some lepidopteran larvae can be significantly attracted by sex pheromones of the same species in a food context. Here we reported that the host-feeding choice of early-instar Mythimna separata larvae can be effectively regulated by the sex pheromone component (Z)-11-hexadecenal (Z11-16: Ald). Further exploration revealed that two olfactory proteins, M. separata general odorant binding protein 2 (MsGOBP2) and olfactory receptor 3 (MsOR3), were molecular basis of the host-feeding choice regulation mediated by Z11-16: Ald. Silencing either MsGOBP2 or MsOR3 led to a sharply reduced preference for Z11-16: Ald-spiked hosts. It is possible that the Z11-16: Ald-based preference of the M. separata larvae for host is governed by the interplay between MsGOBP2 and MsOR3. In the present research, the interactions between MsGOBP2 and Z11-16: Ald were also discussed using molecular dynamics-based approaches. Our research explored insight into the Z11-16: Ald-mediated host-feeding choice regulation of M. separata larvae, all the results would aid in developing olfaction-based methods for controlling pests in larval stage.

Based on the hypothesis that variation of the metabolomes of latex is a response to selective pressure and should thus be affected differently from other organs, their variation could provide insight into the defensive chemical selection of plants. Metabolic profiling was utilized to compare tissues of Euphorbia species collected in various regions. The metabolic variation of latexes was much more limited than that of other organs. In all of the species, the levels of polyisoprenes and terpenoids were found to be much higher in latexes than in leaves and roots. Polyisoprenes were also observed to physically delay the contact and growth of pathogens with plant tissues. A secondary barrier composed of terpenes and, in particular, 24-methylenecycloartanol, exhibited antifungal activity. These results, together with the known roles of the enzymes also present in latexes, demonstrate that they are part of a cooperative defense system that comprises both biochemical and physical elements.

PremisePlant-interacting insects receive plant volatile signals through their antennae, and voltage changes across an antenna exposed to volatile stimuli can be measured to determine if insects can perceive them, often by coupling gas chromatography to electroantennographic detection (GC-EAD). Current methods for analysing GC-EAD data rely on qualitative observation, rather than using quantitative analysis, and are thus prone to bias. Methods and ResultsWe developed a novel quantitative methodology for analysis of GC-EAD data using a signal processing technique on EAD data to compare responses of hawkmoths and bumble bees to a library of common floral volatiles. Responses varied between species and sexes and these responses were in some cases affected by compound type or modification. Our method also works with existing, published GC-EAD datasets. ConclusionsOur novel GC-EAD analysis technique is robust to baseline drift and low signal:noise ratios commonly found in GC-EAD data, and provides a way forward for quantitative studies of plant volatile- mediated plant-insect interactions.

Plants produce diverse secondary compounds as natural protection against microbial and insect attack. Most of these compounds, including bitters and acids, are sensed by insect gustatory receptors (Grs). Acids are potentially toxic to insects, but there are few reports on sour compounds as ligands of insect Grs. Here, using two different heterologous expression systems, the insect Sf9 cell line and the mammalian HEK293T cell line, we started from crude extracts of rice (Oryza sativa) and successfully identified oxalic acid (OA) as a ligand of NlGr23a, a Gr in the brown planthopper Nilaparvata lugens. The antifeedant effect of OA on the brown planthopper was dose dependent, and NlGr23a is essential for OAs antifeedant activity in both artificial diets and rice plants. NlGr23a is also indispensable for tarsal OA sensing. To our knowledge, OA is the first identified ligand starting from plant crude extracts and the first known strong acid for insect Grs. These findings on rice-planthopper interactions will be of broad interest for pest control in agriculture and also for better understanding of how insects select host plants. Research organismNilaparvata lugens

Alphitobius diaperinus (Coleoptera: Tenebrionidae), the lesser mealworm, is one of the most significant pests of the poultry industry worldwide. These insects cause structural damage in poultry houses and transmit several diseases, impacting chickens productivity and rearing costs. Although semiochemicals may offer alternative insect pest management strategies, basic information regarding pheromone identity and their role on the behavioural ecology according to their circadian pattern of sexual behaviour of A. diaperinus is essentially lacking. This study is aimed to analyse the relation of gender identity and sexual experience of adults of A. diaperinus on their mating behaviour and whether this response is related to their CHC profiles secreted. The following steps were taken to achieve the studys goal. First, the circadian pattern of their sexual activity was observed in newly emerged pairs for at least twenty-one days (virgin adults) and experienced adults collected from the field to identify a difference based on their sexual experience and achieve the optimal mating season to develop the following assays. Subsequently, Y-tube olfactometer bioassays were conducted to evaluate their odour bouquet attraction based on gender and sexual experience. Additionally, mating behaviour bioassays were conducted to evaluate the two factor effects. Finally, cuticular analysis was performed using gas chromatography-mass spectrometry to evaluate possible chemical differences based on the two factors. With statistical and multivariate analysis, we found that behavioural, mating and chemical responses are different based on their sexual experience. The mating sequences were described into precopulatory, copulatory and postcopulatory phases. This finding gives us a deeper understanding of the sexual communication during mating. In summary, our findings provide new insights into the mating system and chemical ecology of A. diaperinus. The results presented here may serve as a base for further studies to develop strategies for managing this pest.

In May-June 2019, the microalga Chrysochromulina leadbeateri caused a massive fish-killing event in several fjords in Northern Norway, resulting in the largest direct impact ever on aquaculture in northern Europe due to toxic algae. Motivated by the fact that no algal toxins have previously been described from C. leadbeateri, we set out to investigate the chemical nature and toxicity of secondary metabolites in extracts of two strains (UIO 393, UIO 394) isolated from the 2019 bloom, as well as one older strain (UIO 035) isolated during a bloom in Northern Norway in 1991. Initial LC-DAD-MS/MS-based molecular networking analysis of the crude MeOH extracts of the cultivated strains showed that their profiles of small organic molecules, including a large number of known lipids, were very similar, suggesting that the same class of toxin(s) were likely the causative agents of the two harmful algal bloom (HAB) events. Next, bioassay-guided fractionation using the RTgill-W1 cell line and metabolomics analysis pointed to a major compound affording [M+H]+ ions at m/z 1399.8333 as a possible toxin, corresponding to a compound with the formula C67H127ClO27. Moreover, our study unveiled a series of minor analogues exhibiting distinct patterns of chlorination and sulfation, together defining a new family of compounds, which we propose to name leadbeaterins. Remarkably, these suspected toxins were detected in situ in samples collected during the 2019 bloom close to Tromso, thereby substantiating their likely role in fish kills. The elemental compositions of the putative C. leadbeateri ichthyotoxins strongly indicate them to be long linear polyhydroxylated polyketides, structurally similar to sterolysins, reported from a number of dinoflagellates.

Plants constantly emit volatile organic compounds (VOCs) that can influence the physiology and behavior of neighboring plants. While the role of stress-induced VOCs in mediating plant-plant interactions is well established, the ecological significance of constitutive VOCs from undamaged plants remains less understood. We demonstrate that barley plants can detect the growth rate of their undamaged neighbors through constitutive VOCs and respond by adjusting their trade-off between growth and induced defense. Exposure to volatiles from cultivars with slower or faster growth triggered distinct shifts in biomass accumulation and gene expression in receiver plants, whereas exposure to VOCs from cultivars with similar growth rates elicited negligible responses. These divergent patterns reflect a trade-off between growth and induced defense, consistent with adaptive responses to anticipated competition. Our findings reveal a previously unrecognized adaptive function of constitutive VOCs in mediating receiver growth based on neighbor growth rate, emphasizing their role in shaping plant-plant interactions.

Phytophagous insects are capable of detecting and locating suitable hosts, which emit volatile compounds. Polyphagous species appear to have a complex olfactory strategy given that their numerous hosts have diverse emission profiles. In particular, their hosts volatile emissions share some of the same compounds, providing chemical bridges between them. However, the behavioural plasticity observed in insect host selection suggests that other volatiles have a complementary role. Here we explore how the specialization of polyphagous Tephritidae fruit fly in detecting and discriminating between host fruits has driven their chemical selectivity. The volatile emissions from intact or mechanically damaged fruit of 28 different species were analysed using gas chromatography-mass spectrometry and fed into a neuronal model of an olfactory system. We predicted in silico a functional trade-off between the two tasks, with optimal performance depending on detecting a higher proportion of shared fruit compounds, but with lower sensitivity compared to unshared compounds, or vice-versa. Using triple point electroantennography and a behavioural assay, we studied the olfactory response of Tephritidae fruit fly species that oviposit on fruit. Amplitude of the olfactory responses of eight species were negatively correlated with the compounds degree of sharedness among fruit emissions, while response probability was previously shown to correlate positively with a similar metric. A dose-dependent switch in the flys preference confirmed the ecological importance of both shared and unshared fruit compounds. Thus, we propose that insect olfactory systems are chemically tuned to detect suitable hosts and accurately discriminate between them.

The planthopper Pentastiridius leporinus [Hemiptera: Cixiidae] is a vector of the two plant pathogenic bacteria Candidatus Arsenophonus phytopathogenicus and Candidatus Phytoplasma solani in potato. An infection leads to symptoms such as rubbery and non-processable tubers and consequently to substantial decreases in yield and tuber quality as well as to abandonment of seed potato production in affected areas. Up to date, resistant potato varieties are not yet known, and the tool box of integrated pest management to prevent the spread of P. leporinus as causal vector is quite limited. Mortality experiments designed as no-choice trials on potato cultivar Gala (Solanum tuberosum) and on its wild relative S. bulbocastanum revealed significant effects of the latter on the survival rate of the vector. LC/MS analysis of the insects and their intestines showed that acyl solamines were retrieved only in individuals from the S. bulbocastanum plants. Furthermore, choice-tests were carried out to study the vector behavior. A preference towards S. bulbocastanum vs. S. tuberosum Gala was observed despite its lethal effects. Volatile organic compounds of the two different species were collected and analyzed by GC/MS. The two profiles differed in 39 of 80 compounds. The wild potato species S. bulbocastanum and its compounds are discussed as potential starting points for further research on sustainable management of P. leporinus. Key MessageO_LIWe tested a wild potato against a planthopper which vectors pathogenic bacteria to potato C_LIO_LIWild potato led to higher mortality of the planthopper but was preferred against cultivated potato C_LIO_LIUptake assays suggest that the phloem sucking planthopper is taking up xylem sap as well C_LIO_LIAcyl solamines were only found in guts from planthoppers sucking on the wild potato C_LIO_LIOur results present a starting point for new approaches for sustainable vector control C_LI

O_LIVolatile organic compounds (VOCs) mediate plant-plant signalling and may contribute to phenotypic differentiation among populations. However, the extent to which VOC-mediated signalling varies among locally adapted populations, and how VOC traits relate to major fitness-related traits, remain poorly understood. C_LIO_LIWe conducted a greenhouse experiment using two genetically and phenologically divergent Iberian populations of Arabidopsis thaliana. Plants were exposed to herbivory by Spodoptera exigua, after which we quantified herbivore-induced VOC emissions, VOC-mediated signalling effects on neighbouring conspecifics, and relationships between VOC traits, flowering time, and seed germination. C_LIO_LIHerbivory altered VOC composition, but overall VOC profiles remained broadly similar between populations despite strong divergence in life-history strategies, constitutive resistance to herbivory, and genetic structure. In contrast, correlations between VOC traits and fitness-related traits differed between populations and herbivory treatments. Nevertheless, receiver plants from both populations exhibited reduced herbivore damage after exposure to herbivore-induced emitters, indicating conserved VOC-mediated signalling. C_LIO_LIOur results suggest that herbivore-induced volatile signalling may represent a relatively conserved component of plant defence across locally adapted populations. In contrast, relationships between VOC traits and life-history variation may reflect population-specific integration of defence and fitness-related traits. C_LI