A Verticillium longisporum pleiotropic drug transporter determines tolerance to the plant host beta-pinene monoterpene

Terpenes constitute a major part of secondary metabolites secreted by plants in the rhizosphere. However, their specific functions in fungal-plant interactions have not been investigated thoroughly. In this study we investigated the role of monoterpenes in interactions between oilseed rape (Brassica napus) and the soilborne pathogen Verticillium longisporum. We identified seven monoterpenes produced by B. napus, and production of alpha-pinene, beta-pinene, 3-carene, and camphene was significantly increased upon fungal infection. Among them, beta-pinene was chosen for further analysis. Transcriptome analysis of V. longisporum on exposure to beta-pinene resulted in identification of two highly expressed pleotropic drug transporters paralog genes named VlAbcG1a and VlAbcG1b. Overexpression of VlAbcG1a in Saccharomyces cerevisiae increased tolerance to beta-pinene, while deletion of the VlAbcG1a homologous gene in Verticillium dahliae resulted in mutants with increased sensitivity to certain monoterpenes. Furthermore, the VlAbcG1a overexpression strain displayed an increased tolerance to beta-pinene and increased virulence in tomato plants. Data from this study give new insights into the roles of terpenes in plant-fungal pathogen interactions and the mechanisms fungi deploy to cope with the toxicity of these secondary metabolites

The use of semiochemical mass traps to reduce mirid damage in strawberry crops.

Advances in the identification of attraction of mirids to semiochemicals has provided the opportunity to exploit synthetically produced sex pheromones and plant produced compounds for controlling pest species in crops. Sex pheromones of mirids are important for long range attraction of males to females and plant volatiles indicate egg laying sites for female mirids. The European tarnished plant bug (Lygus rugulipennis) causes large yield losses (10->80%) in conventional and organic strawberry. Following the successful development of these semiochemicals in combination with effective traps we investigated the ability of a mass trapping system to reduce damage in strawberry crops in combination with another strawberry pest, strawberry blossom weevil (Anthonomus rubi). Attractive traps and lures with host plant volatiles and sex or aggregation pheromones were deployed in strawberry crops at 50 per hectare in several European countries. Trap catches were monitored in relation to fruit damage and compared to untreated crops. Traps successfully captured both target pest species. In this paper we will present the results of the potential to reduce crop damage using mass traps and discuss the benefits and difficulties in using these techniques as part of integrated or organic pest management

Odour Maps in the Brain of Butterflies with Divergent Host-Plant Preferences

Butterflies are believed to use mainly visual cues when searching for food and oviposition sites despite that their olfactory system is morphologically similar to their nocturnal relatives, the moths. The olfactory ability in butterflies has, however, not been thoroughly investigated. Therefore, we performed the first study of odour representation in the primary olfactory centre, the antennal lobes, of butterflies. Host plant range is highly variable within the butterfly family Nymphalidae, with extreme specialists and wide generalists found even among closely related species. Here we measured odour evoked Ca2+ activity in the antennal lobes of two nymphalid species with diverging host plant preferences, the specialist Aglais urticae and the generalist Polygonia c-album. The butterflies responded with stimulus-specific combinations of activated glomeruli to single plant-related compounds and to extracts of host and non-host plants. In general, responses were similar between the species. However, the specialist A. urticae responded more specifically to its preferred host plant, stinging nettle, than P. c-album. In addition, we found a species-specific difference both in correlation between responses to two common green leaf volatiles and the sensitivity to these compounds. Our results indicate that these butterflies have the ability to detect and to discriminate between different plant-related odorants

Chemical communication in leaf mining moths of the genus phyllonorycter

Laboratory studies of pheromone release behaviour haverevealed that virgin females of all of the nine species of thegenus Phyllonorycter investigated demonstrated the samepheromone release posture. Their calling activity wasregistered at the beginning of the photophase. This is anunusual time for calling in moths. Our hypothesis is, that thisuncommon timing of the pheromone communication may have beencaused by the sensitivity of the males to sex attractionantagonists, released into the environment by females of otherspecies at other times of the day. The diurnal calling behaviour of virgin Ph. junoniellafemales was more pronounced under a cyclic thermal regime(close to the natural conditions) than under constanttemperature. We assume, that the occurrence of an extra peak inthe pheromone release behaviour as well as the extension of thecalling period to cover the larger part of the light period maybe adaptive for Ph. junoniella with a sex ratio stronglyshifted towards females (8:1 females to males), as it may leadto an increased proportion of males mated. It was found, that the leaf miner moth Ph. emberizaepenellareproduced by parthenogenesis of the thelytoky type. Despite acomplete lack of males, the females demonstrated a callingposture with a sex pheromone release with the typical diurnalrhythm of that behaviour. Theoretical speculations that in thelytoky, where there is no need to attract a sexual partner, thefemales benefit by reducing their sexual behaviour, was notconfirmed for Ph. emberizaepenella. Ten compounds used in the sex communication of fivephyllonoryctid species were identified from calling virginfemales: Z10-, Z8- and E10-14:OAc for Ph. acerifoliella;E10-12:OAc, 12:OAc and E10-12:OH for Ph. blancardella;E8,E10-14:OAc and E8,E10-14:OH for Ph. emberizaepenella;Z8-14:OAc, 14:OAc and Z8-14:OH for Ph.heegerella; as well asZ10-14:OAc for Ph. ulmifoliella. The Solid Phase MicroExtraction technique was applied for the first time to collecta sex pheromone from a single calling microlepidopteran femaleand our data clearly demonstrated the advantages of thismethod. Our field screening tests in Lithuania disclosed new sexattractants for five phyllonoryctid species: E10-12:OH for Ph.sorbi; E10-12:OAc for Ph. cydoniella and Ph.oxyacanthae;Z10-12:OAc for Ph. junoniella; as well as Z10-14:OAc in a 1:10mixture with E9-14:OAc for Ph. acerifoliella. The lattermixture was also found to be a potential sex attractant for Ph.coryli and Ph. heegerella. In addition, field trapping experiments revealed fourteensex attraction antagonists for males of seven Phyllonorycterspecies: E10-12:OH for Ph. acerifoliella and Ph.cydoniella;E10-12:OAc and Z10-14:OAc for Ph. heegerella; Z10-, E10-12:OHand E10-14:OH for Ph. mespilella; Z10-12:OH for Ph.oxyacanthae; Z7-, Z9- and Z10-12:OAc for Ph. sorbi; as well asZ8-, Z9-, E9-, E10- and E11-14:OAc for Ph.ulmifoliella. Schemes of probable interactions by means of allelochemicalsacting between Ph.blancardella and 7 other moth species, Ph.ulmifoliella and 414,Ph. sorbi and 243, Ph.mespilella and 11as well as Ph. acerifoliella and 7 other moth species arepresented. Basing both on our own results and on data published byothers, we conclude that the pheromones used by gracillariidshave appeared at a period lasting between the formation oflower and of higher Heteroneura. Key words: Phyllonorycter, Gracillariidae, Lepidoptera, sexpheromone, sex attractant, sex attraction antagonist, callingbehaviour, calling posture, olfactometer, sex ratio,parthenogenesis, evolution, ecology, Solid Phase MicroExtraction.NR 2014080

Volatiles released from foliar extract of host plant enhance landing rates of gravid Polygonia c-album females, but do not stimulate oviposition

The role of olfactory cues for host search is much less investigated in day-active butterflies than in their relatives, the nocturnal moths. The goal of this study was to investigate whether host-plant volatiles from foliar extracts of hop, Humulus lupulus L. (Cannabaceae), evoke electroantennographic (EAG) responses, increase landing rates, and stimulate egg-laying behavior of gravid Polygonia c-album L. (Lepidoptera: Nymphalidae) females. Eighty-nine volatile compounds were detected in a non-concentrated methanol extract of hop by gas chromatography-mass spectrometry, 11 of which elicited an EAG response. Concentration of the crude extract significantly reduced landing rates on artificial leaves treated with the sample due to loss of volatile compounds, but after landing the oviposition response of gravid females was not affected. A mixture of eight commercially available EAG-active volatiles increased the landing rate of gravid females to their source but did not act as oviposition stimulants. Dividing the volatile compounds into two groups - consisting of (1) hexanal, (E)-2-hexenal, octanal, nonanal, and decanal, and (2) sulcatone, humulene, and benzyl alcohol - obliterated effectiveness, revealing synergism between compounds. Although volatiles did not stimulate oviposition, they significantly contributed to the distribution of eggs by increasing the landing rates on treated artificial leaves

Data from: Selection by parasitoid females among closely related hosts based on volatiles: Identifying relevant chemical cues

Parasitoid fitness is influenced by the ability to overcome host defense strategies and by the ability of parasitoid females to select high-quality host individuals. When females are unable to differentiate among hosts, their fitness will decrease with an increasing abundance of resistant hosts. To understand the effect of mixed host populations on female fitness, it is therefore necessary to investigate the ability of female parasitoids to select among hosts. Here, we used behavioral assays, headspace volatile collection, and electrophysiology to study the ability of Asecodes parviclava to use olfactory cues to select between a susceptible host (Galerucella calmariensis) and a resistant host (Galerucella pusilla) from a distance. Our studies show that parasitoid females have the capacity to distinguish the two hosts and that the selection behavior is acquired through experiences during earlier life stages. Further, we identified two volatiles (α-terpinolene and [E]-β-ocimene) which amounts differ between the two plant–herbivore systems and that caused behavioral and electrophysiological responses. The consequence of this selection behavior is that females have the capacity to avoid laying eggs in G. pusilla, where the egg mortality is higher due to much stronger immune responses toward A. parviclava than in larvae of G. calmariensis

Identification of (Z)-8-Heptadecene and n-Pentadecane as Electrophysiologically Active Compounds in Ophrys insectifera and Its Argogorytes Pollinator

Sexually deceptive orchids typically depend on specific insect species for pollination, which are lured by sex pheromone mimicry. European Ophrys orchids often exploit specific species of wasps or bees with carboxylic acid derivatives. Here, we identify the specific semiochemicals present in O. insectifera, and in females of one of its pollinator species, Argogorytes fargeii. Headspace volatile samples and solvent extracts were analysed by GC-MS and semiochemicals were structurally elucidated by microderivatisation experiments and synthesis. (Z)-8-Heptadecene and n-pentadecane were confirmed as present in both O. insectifera and A. fargeii female extracts, with both compounds being found to be electrophysiologically active to pollinators. The identified semiochemicals were compared with previously identified Ophrys pollinator attractants, such as (Z)-9 and (Z)-12-C27-C29 alkenes in O. sphegodes and (Z)-9-octadecenal, octadecanal, ethyl linoleate and ethyl oleate in O. speculum, to provide further insights into the biosynthesis of semiochemicals in this genus. We propose that all these currently identified Ophrys semiochemicals can be formed biosynthetically from the same activated carboxylic acid precursors, after a sequence of elongation and decarbonylation reactions in O. sphegodes and O. speculum, while in O. insectifera, possibly by decarbonylation without preceding elongation

Acaricidal activity against Ixodes ricinus nymphs of essential oils from the Libyan plants Artemisia herba alba, Origanum majorana and Juniperus phoenicea

Ixodes ricinus (L.) (Acari: Ixodidae) is a major vector for the transmission of several important human pathogens. The aim of the present study was to evaluate the in vitro efficacy of different concentrations of essential oils (Eos) on I. ricinus tick nymphs. Oils were obtained from the leaves of three plants native to Libya: white wormwood (Artemisia herba alba Asso), marjoram (Origanum majorana L.) and Arar (Juniperus phoenicea L., English common name Phoenician juniper). Assays were done using the "open filter paper method". Two concentrations from each oil, 0.5 and 1 mu l/cm, were tested. The acaricidal effect was measured in terms of the lethal concentrations (LC50, LC95) and lethal time (LT50, LT95). Mortality rates were obtained by counting the surviving nymphs every 30 min for the first five hours and then at 24, 48 and 72 h. A mortality of 100% was recorded at the higher concentration of oils (1 mu l/cm(2)) from A. herba alba and J. phoenicea at the first 2 h of exposure. Exposure to O. majorana led to 100% mortality on the third day (72 h), and this effect decreased noticeably with 0.5 mu l/cm(2) oil at the same exposure time. However, 50% of ticks showed a paralysis effect and less movement after 2 h. The LC50 of mortality was reached within the first 24 h of exposure time at 0.5 mu l/cm(2) of O. majorana, which produced 60% tick's mortality. Chemical composition of the essential oils was elucidated by gas chromatography-mass spectrometry analyses. These results suggest that essential oils deserve further investigation as components of alternative approaches for I. ricinus tick control

The repellency and toxicity effects of Essential oils from the Libyan plants Salvadora persica and Rosmarinus officinalis against nymphs of Ixodes ricinus.

Essential oils extracted from the leaves of Libyan Rosemary (Rosmarinus officinalis L.), and Miswak (Salvadora persica L.) were evaluated for their acaricidal and repellent effects on Ixodes ricinus L. nymphs (Acari: Ixodidae) using a bioassay based on an “open filter paper method".  R. officinalis leaf essential oil diluted to 0.5 and 1µl/cm ² in acetone exhibited, respectively, 20% and 100% tick mortality after about 5 hours of exposure. A total of 50% and 95% of I. ricinus nymphs were killed by direct contact with the oil when exposed to lethal concentrations (LC) of 0.7µl/cm² (LC50) and 0.95 µl/cm² (LC95), respectively. The LC50 (0.5µl/cm²) was reached before the end of the first 24 hours of exposure time (ET), as tick mortality at 24 hours was 60%. S. persica leaf essential oil at 1µl/cm² showed a significant repellency effect against I. ricinus nymphs at 1.5 hours ET. A 95% repellency was observed at a repellent concentration (RC95) of 1µl/cm² of S. persica, but no significant mortality was recorded at this dose of S. persica oil. Gas chromatography-mass spectrometry analyses showed that the main monoterpenes in both oils were 1,8-cineol, α-pinene, and β-pinene, although in markedly different proportions. These results suggest that essential oils have substantial potential as alternative approaches for I. ricinus tick control