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Guerin, Patrick

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Guerin, Patrick
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patrick.guerin@unine.ch
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https://libra.unine.ch/handle/123456789/310

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  • Publication
    Métadonnées seulement
    Plant volatile compounds shorten reaction time and enhance attraction of the codling moth (Cydia pomonella) to codlemone
    (2012)
    Schmera, D.
    ;
    Guerin, Patrick 
    BACKGROUND: The codling moth is the most serious pest of deciduous tree fruit (apples, pears, crabapples, walnuts, quince) worldwide. The high frequency of insecticide treatments per season has resulted in breakdown of codling moth control owing to insecticide resistance. As an alternative, integrated pest management includes mating disruption to achieve population suppression in orchards. Under this scheme, the sex pheromone of the codling moth, (E, E)-8,10-dodecadien-1-ol (codlemone), is released from dispensers in crops to hinder mating by luring males. Increasing the attractiveness of codlemone formulations to codling moth males can be regarded as a key to increasing the efficacy of mating disruption. With this aim, the effects of adding plant volatiles on the behavioural responses of codling moth males to codlemone were tested. RESULTS: Adding R(+)-limonene, linalool, (E)-beta-farnesene or ethyl (E, Z)-2,4-decadienoate to codlemone significantly increases the proportion of males flying to the pheromone source in a wind tunnel. The response level is equivalent to that of males responding to females releasing codlemone. Using real-time recordings, it is shown how these four plant products also shorten the response time of males to codlemone under the behavioural criteria time to activation, time till upwind flight is induced and time to pheromone source contact. CONCLUSION: Shortening the response time and increasing source location by males of dispensers releasing codlemone with R(+)-limonene, linalool, (E)-beta-farnesene or ethyl (E, Z)-2,4-decadienoate added would enhance mating disruption through better engagement ofmales with dispensers, to the detriment of females. (C) 2011 Society of Chemical Industry
  • Publication
    Métadonnées seulement
    The NCCR Plant Survival at the University of Neuchatel - The role of chemistry in an interdisciplinary Swiss research network
    (2003)
    Vogelgsang, Susanne
    ;
    Abou-Mansour, Eliane
    ;
    Guerin, Patrick 
    ;
    Hoballah, Maria Elena
    ;
    Turlings, Ted 
    ;
    Tabacchi, Raffaele
    The survival of plants is of fundamental importance to guarantee the biodiversity in natural areas and a sustainable agriculture. The National Centre of Competence in Research 'Plant Survival in Natural and Agricultural Ecosystems' devotes its research efforts to the understanding of mechanisms of plant survival. The mechanisms that plants employ to adapt to their biotic and abiotic environment and to cope with important stress factors are investigated. This is achieved by interdisciplinary interaction of disciplines within the NCCR. The particular role played by natural products and analytical chemistry in seven different projects is summarized.
  • Publication
    Métadonnées seulement
    Fabrication of an olfactometer for mosquito behavioural studies
    (2010)
    Omrani, S. M.
    ;
    Vatandoost, H.
    ;
    Oshaghi, M. A.
    ;
    Shokri, F.
    ;
    Guerin, Patrick 
    ;
    Ershadi, M. R. Y.
    ;
    Rassi, Y.
    ;
    Tirgari, S.
    Background & objectives: Olfaction is the major sensory modality involved in the resource searching behaviour of insects including vector mosquitoes (Diptera: Culicidae). To date, our current country-wide knowledge on the host-seeking behaviour of Iranian mosquitoes is mainly confined to host preference which has exclusively come from field studies. Olfactometer is a scientific tool by which more naive aspects of man-vector contact can be clarified under controlled and less biased conditions. Methods: The wind tunnel and stimulus delivery system was constructed from acrylic materials based on previously introduced models with some modifications. Air supply and required light were ensured by a powerful compressor and incandescent bulbs, respectively. Desired level of temperature was maintained by controllable heating radiators. For humidity production a unique in-built piezo system was devised in the course of the air flow. Fine regulators facilitated the continuous generatation of the humidity at a preset level. Results: Titanium tetrachloride smoke plus monitoring of the wind speed revealed that the flow of air was proper and invariable. A desired level of humidity and temperature could be set up in just 10 and 15-45 min, respectively. These physical parameters varied only +/-2% (humidity) and +/-0.15 degrees C (temperature) in a typical 20 min duration. Conclusion: The first sophisticated olfactometer in the field of medical entomology in Iran is reported here. Fast set up and stability of physical parameters are its salient features. It is expected that with the aid of this olfactometer further information on the physiological principles of the host-seeking behaviour of mosquitoes become available soon.
  • Publication
    Métadonnées seulement
    Components from Sri Lankan Piper betle L. leaf oil and their analogues showing toxicity against the housefly, Musca domestica
    (2007)
    Mohottalage, Susantha
    ;
    Tabacchi, Raffaele
    ;
    Guerin, Patrick 
    The essential oil extracted from Piper betle L. leaf using pilot plant steam distillation was tested against the adult housefly, Musca domestica, for insecticidal activity. LC50 values at the end of 24 and 48 h exposure periods were 10.3 and 8.7 mg/dm(3), respectively. Ceylon citronella oil (Cymbopogon nardus) used as a standard showed LC(50)s of 26.5 and 24.2 mg/dm(3) for the same exposure periods. Bioassay-guided fractionation of P. betle leaf oil revealed safrole and eugenol as the active principles against M. domestica, safrole showing LC50 values of 4.8 and 4.7 mg/dm(3), and eugenol 7.3 and 6.2 mg/dm(3) for the 24 and 48 h exposure periods, respectively, while citronellal (synthetic standard) showed equal LC50 values of 14.3 mg/dm(3) for the same exposure periods. Using safrole as the starting compound, eight analogues were prepared to study structure-activity relationships. Among the eight analogues, dihydrosafrole gave almost equal mortality at LC50 4.7 mg/dm(3) as that of the parent compound safrole after 24 and 48 h exposure, but isosafrole was twice as active as safrole, showing LC50 values of 2.3 and 2.2 mg/dm(3) for the 24 and 48 h exposure periods. Our GC-MS studies on Sri Lankan P. betle leaf oil show that it contains safrole (52.7%), allyllpyrocatechol diacetate (15.4%), eugenol (6.4%) and eugenyl acetate (5.8%) as the major components. Here we also present the GC-MS profile of fractions of Sri Lankan P. betle leaf oil. Copyright (c) 2006 John Wiley & Sons, Ltd.
  • Publication
    Métadonnées seulement
    Oriented responses of grapevine moth larvae Lobesia botrana to volatiles from host plants and an artificial diet on a locomotion compensator
    (2009)
    Becher, P. G.
    ;
    Guerin, Patrick 
    Larvae of the grapevine moth Lobesia botrana (Lepidoptera: Tortricidae) are a major pest of vine, Vitis vinifera. As larvae have limited energy reserves and are in danger of desiccation and predation an efficient response to plant volatiles that would guide them to food and shelter could be expected. The responses of starved 2nd or 3rd instar larvae to volatile emissions from their artificial diet and to single host plant volatiles were recorded on a locomotion compensator. Test products were added to an air stream passing over the 30 cm diameter servosphere. The larvae showed non-directed walks of low rectitude in the air stream alone but changed to goal-oriented upwind displacement characterised by relatively straight tracks when the odour of the artificial diet and vapours of methyl salicylate, 1-hexanol, (Z)-3-hexen-1-ol, terpinen-4-ol, 1-octen-3-ol, (E)-4,8-dimethyl-1,3,7-nonatriene and (Z)-3-hexenyl acetate were added to the air stream. This chemoanemotactic targeted displacement illustrates appetence for certain volatile cues from food by starved Lobesia larvae. Analysis of the larval behaviour indicates dose dependent responses to some of the host plant volatiles tested with a response to methyl salicylate already visible at 1 ng, the lowest source dose tested. These behavioural responses show that Lobesia larvae can efficiently locate mixtures of volatile products released by food sources as well as single volatile constituents of their host plants. Such goal-oriented responses with shorter travel time and reduced energy loss are probably of importance for larval survival as it decreases the time they are exposed to biotic and abiotic hazards. (C) 2009 Elsevier Ltd. All rights reserved.
  • Publication
    Métadonnées seulement
    Pollinator Choice in Petunia Depends on Two Major Genetic Loci for Floral Scent Production
    (2011)
    Klahre, U.
    ;
    Gurba, A.
    ;
    Hermann, K.
    ;
    Saxenhofer, M.
    ;
    Bossolini, E.
    ;
    Guerin, Patrick 
    ;
    Kuhlemeier, C.
    Background: Differences in floral traits, such as petal color, scent, morphology, or nectar quality and quantity,. can lead to specific interactions with pollinators and may thereby cause reproductive isolation. Petunia provides an attractive model system to study the role of floral characters in reproductive isolation and speciation. The night-active hawkmoth pollinator Manduca sexta relies on olfactory cues provided by Petunia axillaris. In contrast, Petunia exserta, which displays a typical hummingbird pollination syndrome, is devoid of scent. The two species can easily be crossed in the laboratory, which makes it possible to study the genetic basis of the evolution of scent production and the importance of scent for pollinator behavior. Results: In an F2 population derived from an interspecific cross between P. axillaris and P. exserta, we identified two quantitative trait loci (QTL) that define the difference between the two species' ability to produce benzenoid volatiles. One of these loci was identified as the MYB transcription factor ODORANT1. Reciprocal introgressions of scent QTL were used for choice experiments under controlled conditions. These experiments demonstrated that the hawkmoth M. sexta prefers scented plants and that scent determines choice at a short distance. When exposed to conflicting cues of color versus scent, the insects display no preference, indicating that color and scent are equivalent cues. Conclusion: Our results show that scent is an important flower trait that defines plant-pollinator interactions at the level of individual plants. The genetic basis underlying such a major phenotypic difference appears to be relatively simple and may enable rapid loss or gain of scent through hybridization.
  • Publication
    Métadonnées seulement
    Contact chemostimuli in the mating behaviour of the cattle tick, Boophilus microplus
    (1998)
    De Bruyne, Marien
    ;
    Guerin, Patrick 
    Mating of the cattle tick Boophilus microplus is mediated by chemical stimuli on the cuticle of females. Males are arrested on the dorsum of females attached to the host, frequently sample the substrate, and then tip-over to the ventrally located gonopore. These behaviours are also observed in vitro when males are placed on a small glass bead treated with a female extract. Time spent and tip-ever by male ticks on dummies is used in an assay to test the behavioural significance of fractions of the extract. TLC separation yields one apolar fraction that arrests males, though much less so than the whole extract, but lost tip-over behaviour This apolar fi action contains a series of cholesteryl esters that, when tested individually, show no arrestment activity at levels present in the extract but, when combined, are as active as the fraction. When a small silica column is used for fractionation, all biological activity is reproduced after recombining the fractions. In addition to the early eluting apolar fraction containing cholesteryl esters, a set of highly active more polar fractions is isolated. Electrophysiological recordings from gustatory sensilla on the pedipalps of male B. microplus, which are regularly brought into contact with the cuticle of the female during mating, provide evidence for receptors in two of them responding to the whole extract and to the behaviourally active polar fractions. Mating behaviour involving arrestment and tip-over is clearly initiated by a mixture of chemical stimuli, and tip-over behaviour is associated with the more polar material. Arch. Insect Biochem. Physiol. 39:65-80, 1998. (C) 1998 Wiley-Liss, Inc.
  • Publication
    Métadonnées seulement
    In vitro assays for repellents and deterrents for ticks: differing effects of products when tested with attractant or arrestment stimuli
    (2003)
    McMahon, Conor
    ;
    Kroeber, Thomas 
    ;
    Guerin, Patrick 
    Most in vivo and in vitro tests with repellents or deterrents against ticks have not considered which sensory channel is being targeted. We have recorded the responses of two hard tick species (Acari: Ixodidae) in vitro to determine if such products can disrupt the perception of an attractant in a repellent assay or the perception of an arrestment stimulus in a deterrent assay. Ethyl butylacetylaminopropionate (EBAAP), N,N-diethyl-methyl-benzamide (deet), permethrin and indalone were chosen to test their capacity to inhibit the attraction of Amblyomma variegatum Fabricius to its aggregation-attachment pheromone. Vapours of each test product plus those from a synthetic blend of the pheromone were delivered to the walking tick in an air stream on a locomotion compensator. Neither EBAAP, deet, permethrin nor indalone could inhibit attraction of A. variegatum even when each of the test products was delivered at 10(6) times the pheromone. Indalone did decrease the attraction of A. variegatum to the pheromone and induced repulsion of A. variegatum when presented on its own in the air stream. The effect of permethrin, a sodium channel blocker, was also tested in a deterrent assay measuring the arrestment of Ixodes ricinus (L.) adults on its own faeces and faecal constituents. Permethrin deterred arrestment at doses of 670 fg/cm(2) to 67 ng/cm(2), i.e. at levels five times lower than the dose of chemostimuli present in the arrestment stimulus. This sensitivity to permethrin suggests that it acts via the contact chemoreception channel.
  • Publication
    Métadonnées seulement
    Responses of the tropical bont tick, Amblyomma variegatum (Fabricius), to its aggregation-attachment pheromone presented in an air stream on a servosphere
    (2000)
    McMahon, Conor
    ;
    Guerin, Patrick 
    Male Amblyomma variegatum ticks feeding on a host release a mixture of o-nitrophenol and methyl salicylate which serves to attract conspecifics. The behavioural responses of A. variegatum on a servosphere to these volatiles presented in an air stream are detailed hers. In still air, ticks walked on all eight legs, but with long halts. In contrast, the air stream caused continuous walking and induced a reaching response where the forelegs actively sampled the air. Such reaching increased the angular velocity and reduced walking speed, effects that were amplified in the presence of vapours from o-nitrophenol and methyl salicylate in the air flowing over the ticks. Vapour from a 1:1 mixture of o-nitrophenol and methyl salicylate was attractive over a 10(4)-fold concentration range providing an increase in upwind displacement of 20-40%, significantly higher than the natural ratio where o-nitrophenol vapour predominates. Although the responses to o-nitrophenol vapour were variable when presented alone, this chemical was consistently attractive when delivered with steer hair odour - unattractive on its own. Moreover, the upwind walk to this combination did not cause a change in speed or angular velocity. This supports the hypothesis that the response to the pheromone is enhanced by host odour.
  • Publication
    Métadonnées seulement
    A standardised in vivo and in vitro test method for evaluating tick repellents
    (2013)
    Kroeber, Thomas 
    ;
    Bourquin, Martine 
    ;
    Guerin, Patrick 
    The threat of transmission of Lyme borelliosis and tick-borne encephalitis by ixodid ticks has resulted in an increasing number of tick repellents coming onto the market. To allow proper evaluation of the efficacy of different types of compounds and their formulations, there is a need for standardised methods for testing ticks repellents. Ticks show a marked negative geotactic response following contact with a potential host, i.e., they climb up in order to locate attachment and feeding sites, whereas exposing ticks to repellents induces positive geotaxis, i.e., ticks walk downwards or drop off the treated host or substrate. We describe here complementary tests that employ these geotactic responses to evaluate repellents: one in vitro on a warm glass plate and the other on the lower human leg (shin). The compounds tested were DEET, EBAAP, icaridin, capric acid, lauric acid, geraniol, citriodiol, citronella essential oil and lavender essential oil, all non-proprietary ingredients of widely distributed tick repellent formulations. In controls on both the warm glass plate and the human leg, the majority of Nodes ricinus nymphs walk upwards. By contrast, in both the in vitro and in vivo tests, effective doses of repellents cause ticks to either walk downwards or fall off the substrates, termed here "affected ticks". The ED75 values for affected ticks on the human leg indicate that the test products can be divided into three groups: (1) icaridin, EBAAP, DEET and capric acid with values between 0.013 and 0.020 mg/cm(2), (2) citriodiol and lauric acid with values between 0.035 and 0.058 mg/cm(2), and (3) geraniol, citronella oil and lavender essential oil with values between 0.131 and 1.58 mg/cm2. The latter three products can be considered as less effective repellents. The tests on the warm glass plate resulted in very similar efficacy rankings for the products tested in vivo, and the ticks' behavioural responses also corresponded closely to those observed on the treated human leg. The ED75 values on the glass plate ranged from half to one sixth needed on the leg. The warm glass plate test thus provides a reliable alternative to human subjects for an initial evaluation of new repellents, and is particularly appropriate for testing products with still to be determined human toxicity and dermatological effects. (C) 2013 Elsevier Inc. All rights reserved.