Evaluating the Induced-Odour Emission of a Bt Maize and its Attractiveness to Parasitic Wasps |
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Authors: | Email author" target="_blank">Ted?CJ?TurlingsEmail author Philippe?M?Jeanbourquin Matthias?Held Thomas?Degen |
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Institution: | (1) Laboratoire d’Ecologie Animale et Entomologie, Institut de Zoologie, Université de Neuchatel, Case Postale 2, 2007 Neuchatel, Switzerland;(2) Station fédérale de recherches en production végétale, 1260 Changins, Nyon, Switzerland |
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Abstract: | The current discussion on the safety of transgenic crops includes their effects on beneficial insects, such as parasitoids
and predators of pest insects. One important plant trait to consider in this context is the emission of volatiles in response
to herbivory. Natural enemies use the odours that result from these emissions as cues to locate their herbivorous prey and
any significant change in these plant-provided signals may disrupt their search efficiency. There is a need for practical
and reliable methods to evaluate transgenic crops for this and other important plant traits. Moreover, it is imperative that
such evaluations are done in the context of variability for these traits among conventional genotypes of a crop. For maize
and the induction of volatile emissions by caterpillar feeding this variability is known and realistic comparisons can therefore
be made. Here we used a six-arm olfactometer that permits the simultaneous collection of volatiles emitted by multiple plants
and testing of their attractiveness to insects. With this apparatus we measured the induced odour emissions of Bt maize (Bt11,
N4640Bt) and its near-isogenic line (N4640) and the attractiveness of these odours to Cotesia marginiventris and Microplitis rufiventris, two important larval parasitoids of common lepidopteran pests. Both parasitoid species were strongly attracted to induced
maize odour and neither wasp distinguished between the odours of the transgenic and the isogenic line. Also wasps that had
previously experienced one of the odours during a successful oviposition divided their choices equally between the two odours.
However, chemical analyses of collected odours revealed significant quantitative differences. The same 11 compounds dominated
the blends of both genotypes, but the isogenic line released a larger amount of most of these. These differences may be due
to altered resource allocation in the transgenic line, but it had no measurable effect on the wasps’ behaviour. All compounds
identified here had been previously reported for maize and the differential quantities in which they were released fall well
within the range of variability observed for other maize genotypes. |
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Keywords: | Bacillus thuringiensis maize parasitoids tritrophic interactions Zea mays |
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