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Degen, Thomas

Nom
Degen, Thomas
Affiliation principale
Email
thomas.degen@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/354
_
0000-0003-2101-2433

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  • Publication
    Métadonnées seulement
    Differential performance and parasitism of caterpillars on maize inbred lines with distinctly different herbivore-induced volatile emissions
    (2012-3-29)
    Degen, Thomas 
    ;
    Bakalovic, N.
    ;
    Bergvinson, D.
    ;
    Turlings, Ted 
    Plant volatiles induced by insect feeding are known to attract natural enemies of the herbivores. Six maize inbred lines that showed distinctly different patterns of volatile emission in laboratory assays were planted in randomized plots in the Central Mexican Highlands to test their ability to recruit parasitic wasps under field conditions. The plants were artificially infested with neonate larvae of the fall armyworm Spodoptera frugiperda, and two of its main endoparasitoids, Campoletis sonorensis and Cotesia marginiventris, were released in the plots. Volatiles were collected from equally treated reference plants in the neighbourhood of the experimental field. The cumulative amount of 36 quantified volatile compounds determined for each line was in good accordance with findings from the laboratory; there was an almost 15-fold difference in total emission between the two extreme lines. We found significant differences among the lines with respect to the numbers of armyworms recovered from the plants, their average weight gain and parasitism rates. Average weight of the caterpillars was negatively correlated with the average total amount of volatiles released by the six inbred lines. However, neither total volatile emission nor any specific single compound within the blend could explain the differential parasitism rates among the lines, with the possible exception of (E)-2-hexenal for Campoletis sonorensis and methyl salicylate for Cotesia marginiventris. Herbivore-induced plant volatiles and/or correlates thereof contribute to reducing insect damage of maize plants through direct plant defence and enhanced attraction of parasitoids, alleged indirect defence. The potential to exploit these volatiles for pest control deserves to be further evaluated.
  • Publication
    Métadonnées seulement
    High genetic variability of herbivore-induced volatile emission within a broad range of maize inbred lines
    (2004)
    Degen, Thomas 
    ;
    Dillmann, Christine
    ;
    Marion-Poll, Frédéric
    ;
    Turlings, Ted 
    Maize plants (Zea mays) attacked by caterpillars release a mixture of odorous compounds that attract parasitic wasps, natural enemies of the herbivores. We assessed the genetic variability of these induced volatile emissions among 31 maize inbred lines representing a broad range of genetic diversity used by breeders in Europe and North America. Odors were collected from young plants that had been induced by injecting them with caterpillar regurgitant. Significant variation among lines was found for all 23 volatile compounds included in the analysis: the lines differed enormously in the total amount of volatiles emitted and showed highly variable odor profiles distinctive of each genotype. Principal component analysis performed on the relative quantities of particular compounds within the blend revealed clusters of highly correlated volatiles, which may share common metabolic pathways. European and American lines belonging to established heterotic groups were loosely separated from each other, with the most clear-cut difference in the typical release of (E)-beta-caryophyllene by European lines. There was no correlation between the distances among the lines based on their odor profiles and their respective genetic distances previously assessed by neutral RFLP markers. This most comprehensive study to date on intraspecific variation in induced odor emission by maize plants provides a further example of the remarkably high genetic diversity conserved within this important crop plant. A better understanding of the genetic control of induced odor emissions may help in the development of maize varieties particularly attractive to parasitoids and other biological control agents and perhaps more repellent for herbivores.
  • Publication
    Métadonnées seulement
    The chemical ecology of plant-caterpillar-parasitoid interactions
    (Cambridge: Cambridge University Press, 2002)
    Turlings, Ted 
    ;
    Gouinguene, Sandrine 
    ;
    Degen, Thomas 
    ;
    Fritzsche-Hoballah, Maria Elena
    ;
    Tscharntke, Teja
    ;
    Hawkins, Bradford