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Turlings, Ted

Nom
Turlings, Ted
Affiliation principale
Fonction
Professeur ordinaire
Email
ted.turlings@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/330

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  • Publication
    Accès libre
    The key to success: host plant adaptations in the root herbivore 'Diabrotica virgifera virgifera'
    (2012)
    Robert, Christelle A.M
    ;
    Turlings, Ted 

    Antagonistic interactions between plants and insects are likely the drivers of a fascinating coevolutionary arms race between the two trophic levels. Plants- and plant breeders- are continuously developing traits that allow them to fend-off herbivores, while phytophagous insect keep inventing counter-adaptations to withstand plant defenses. Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) is a specialist root herbivore of maize, Zea mays. Known as the billion dollar bug in the USA, the rootworm causes important crop damage annually, and no pest management strategy seems to effectively restrain its spread and voracity.

    This thesis aimed at investigating the interactions of D. virgifera larvae with their plant host to underpin the mechanisms of their remarkable ecological success.

    My results show that the root herbivore is able to exploit plant volatiles such as (E)--caryophyllene and ethylene, to assess the host plant quality at a distance and to orient towards optimal hosts (Chapter 1). I also found that D. virgifera can exploit direct plant defenses: The herbivore is able to detect the most nutritious root tissues using differences in 1,4-benzoxazin-3-one profiles (Chapter 3). Furthermore, I show that D. virgifera induces a reconfiguration of the plant primary metabolism and an attenuation of its defensive inducibility, resulting in induced susceptibility (Chapter 4). Induced susceptibility may explain the benefits for the larvae to aggregate in field. By investigating the aggregative behavior of the larvae, I found that D. virgifera uses (E)--caryophyllene in a dosedependent manner to evaluate the density of conspecifics feeding on a plant. The perception of the sesquiterpene allows the insect to aggregate on plants infested with optimal densities of conspecifics, thereby avoiding intraspecific competition and overexploitation (Chapter 4).

    Maize plants seem to be maladapted to D. virgifera. Yet, plant breeders have grown maize plants in the presence of D. virgifera for almost 10 000 years now. It is therefore hardly conceivable that breeding would not have led to selection of resistant germplasm. For instance, the emissions of (E)--caryophyllene was altered and lost in American maize varieties, possibly to reduce the capacity of D. virgifera to aggregate. My work highlights the ecological and physiological costs associated with the emission of this compound, and proposes a novel scenario to explain the evolution of (E)--caryophyllene (Chapter 2). Finally, one resistance trait that would not exert any pressure on the pest that would cause to adapt is herbivore-induced tolerance. I investigated this trait in maize plant and highlight an unexpected role of stems as storage organs for plants under attack (Chapter 5). Focusing on tolerance mechanisms rather than resistance may be a promising avenue to reduce the impact of D. virgifera on maize yield and food production.
  • Publication
    Accès libre
    Systemic root signalling in a belowground, volatile-mediated tritrophic interaction
    (2011)
    Hiltpold, Ivan 
    ;
    Erb, Matthias 
    ;
    Robert, Christelle Aurélie Maud
    ;
    Turlings, Ted 
    Plants attacked by leaf herbivores release volatile organic compounds (VOCs) both locally from the wounded site and systemically from non-attacked tissues. These volatiles serve as attractants for predators and parasitoids. This phenomenon is well described for plant leaves, but systemic induction of VOCs in the roots has remained unstudied. We assessed the spatial and temporal activation of the synthesis and release of (E)-β-caryophyllene (EβC) in maize roots upon feeding by larvae of Diabrotica virgifera virgifera, as well as the importance of systemically produced EβC for the attraction of the entomopathogenic nematode Heterorhabditis megidis. The production of EβC was found to be significantly stronger at the site of attack than in non-attacked tissues. A weak, but significant, increase in transcriptional activity of the EβC synthase gene tps23 and a corresponding increase in EβC content were observed in the roots above the feeding site and in adjacent roots, demonstrating for the first time that herbivory triggers systemic production of a volatile within root systems. In belowground olfactometers, the nematodes were significantly more attracted towards local feeding sites than systemically induced roots. The possible advantages and disadvantages of systemic volatile signalling in roots are discussed.
  • Publication
    Accès libre
    Comparative susceptibility of larval instars and pupae of the western corn rootworm to infection by three entomopathogenic nematodes
    (2009)
    Kurtz, B.
    ;
    Hiltpold, Ivan 
    ;
    Turlings, Ted 
    ;
    Kuhlmann, Ulrich
    ;
    Toepfer, Stefan
    As a first step towards the development of an ecologically rational control strategy against western corn rootworm (WCR; Diabrotica virgifera virgifera LeConte, Coleoptera: Chrysomelidae) in Europe, we compared the susceptibility of the soil living larvae and pupae of this maize pest to infection by three entomopathogenic nematode (EPN) species. In laboratory assays using sand-filled trays, Heterorhabditis bacteriophora Poinar and H. megidis Poinar, Jackson & Klein (both Rhabditida: Heterorhabditidae) caused comparable mortality among all three larval instars and pupae of D. v. virgifera. In soil-filled trays, H. bacteriophora was slightly more effective against third larval instars and pupae, and H. megidis against third larval instars, compared to other developmental stages. In both sand and soil, Steinernema feltiae (Filipjev) (Rh.: Steinernematidae) was least effective against second instars. In conclusion, all larval instars of D. v. virgifera show susceptibility to infection by all three nematodes tested. It is predicted that early application against young larval instars would be most effective at preventing root feeding damage by D. v. virgifera. Applications of nematodes just before or during the time period when third instars are predominant in the field are likely to increase control efficacy. According to our laboratory assays, H. bacteriophora and H. megidis appear to be the most promising candidates for testing in the field.