Systemically-induced response of cabbage plants against a specialist herbivore, Pieris brassicae |
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Authors: | Letizia Mattiacci Sara Rudelli Bettina Ambühl Rocca Sem Genini Silvia Dorn |
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Institution: | (1) Institute of Plant Sciences/Applied Entomology, Swiss Federal Institute of Technology (ETH), Clausiusstrasse 25/NW, CH-8092 Zurich, Switzerland, e-mail: letizia.mattiacci@ipw.agrl.ethz.ch, CH |
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Abstract: | Summary. Plant responses to herbivory might directly affect the herbivore (“direct” defences) or might benefit the plant by promoting
the effectiveness of natural antagonists of the herbivores (“indirect” defences). Brussels sprouts attacked by Pieris brassicae larvae release volatiles that attract a natural antagonist of the herbivores, the parasitoid Cotesia glomerata, to the damaged plant. In a previous study, we observed that feeding by caterpillars on the lower leaves of the plant triggers
the systemic release of volatiles detectable by the parasitoids from upper leaves of the same plant.?The role of these systemically
induced volatiles as indirect defence and the dynamics of their emission were investigated in wind-tunnel dual choice tests
with C. glomerata. The systemically induced emission of volatiles varied depending on leaf age and on plant age. Systemic induction affected
parasitoid effectiveness, as induced plants could be more easily located by parasitoids than non-induced ones.?The role of
the systemic induction as a direct defence was investigated through behavioural and feeding tests with P. brassicae. In dual choice assays, 1st instar larvae preferred to feed and fed more on systemically induced than on non-induced leaves.
In single choice assays, the leaf area consumed by caterpillars was larger on systemically induced leaves than on non-induced
control leaves. However, caterpillars fed on systemically induced leaves attained the same weight as those feeding on non-induced
controls. In addition, P. brassicae pupae whose larvae were fed on systemically induced leaves had longer developmental times than those of larvae fed on non-induced
leaves. Adult oviposition behavior was not influenced by systemic induction.?We conclude that systemically induced responses
in cabbage might reduce P. brassicae fitness both directly, by affecting their development and feeding behavior and indirectly by making caterpillars and pupae
more vulnerable to attack by carnivores. The occurrence of a possible relationship between direct and indirect defence is
discussed.
Received 24 January 2001; accepted 3 May 2001. |
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Keywords: | , Tritrophic interactions —, defence-mechanisms —, induction —, tritrophic interactions —, plant age —, plant induced,,,,,defence —, herbivore damage —, behavior |
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