New insights in analysing parasitoid attracting synomones: early volatile emission and use of stir bar sorptive extraction

Abstract

Summary. It is well known that feeding by Pieris brassicae caterpillars on cabbage leaves triggers the release of volatiles that attract natural antagonists such as the parasitoid Cotesia glomerata. The temporal dynamics in the emissions of parasitoid attracting volatiles has never been elucidated in this system. In a time course experiment, caterpillar infested leaves attracted the parasitoid within one hour after infestation. At such an early stage of infestation, as much as fifty percent of the parasitoids flew towards the infested plant in a wind tunnel bioassay, while only five percent flew towards the non-infested control plant. Three hours after infestation and later, the response to the volatiles from the infested plant reached its maximum and then continued at a constantly high level for the remaining 14 hours of the experiment. Chemical analyses of volatiles collected from infested leaves at short time intervals during the first 24 hours identified a total of ten compounds, comprising green leaf volatiles, terpenoids, and a nitrile. Significant increase of emission within the first 5 hours following initial herbivory was detected for (Z)-3-hexen-1-ol, (Z)-3-hexen-1-yl acetate, cineole and benzylcyanide. Subsequently, a coupled bioassay-chemical analysis procedure was developed allowing for testing and analyzing the same sample for future identification of the bioactive compounds. This was achieved by using stir bar sorptive extraction for the analysis of solvent extracts of caterpillar-damaged leaves.

Plant-mediated effects in the Brassicaceae on the performance and behaviour of parasitoids

“…Plant allelolochemicals are often phylogenetically conserved in specific plant families or genera, such as glucosinolates (hereafter GS) in the Brassicaceae (Rosenthal and Berenbaum 1992;Schoonhoven et al 2005). Chemicals that promote the effectiveness of natural enemies involve volatile compounds that are produced in response to herbivore feeding damage, so-called herbivore induced-plant volatiles (HIPV).…”

The Role of Indole and Other Shikimic Acid Derived Maize Volatiles in the Attraction of Two Parasitic Wasps

“…Although some of these compounds are constitutively emitted by undamaged, healthy plants, considerably higher amounts are emitted after herbivore damage and various HIPVs may even be synthesized de novo in response to damage (Turlings et al, 1990Paré and Tumlinson, 1997). Some HIPVs are specific to certain plant taxa, for example, sulfur containing compounds in Allium plants (Dugravot et al, 2004) or glucosinolate breakdown products in Brassicaceae species (Scascighini et al, 2005), but others are common to many species (Fritzsche Hoballah et al, 2002;van den Boom et al, 2004). Common compounds include "green-leaf volatiles" (C 6 aldehydes, alcohols, and derivatives), cyclic and acyclic terpenoids, phenolic compounds, and nitrogenous compounds (Dicke, 1999;Paré and Tumlinson, 1997).…”

Precise Manipulation Through a Modeling Study

“…The induced volatiles can evoke a range of behavioral responses. They result not only in the attraction of parasitic wasps that attack the caterpillars (Scascighini et al 2005), but also in the attraction of Plutella xylostella moths for whom the Pieris-infested plant provides enemy-free space (Shiojiri et al 2002).…”

“…However, after herbivores have been eliminated, continuation of the emission is no longer needed for the plant, and if the emission continues, this is likely to devaluate the volatiles as a signal to carnivorous arthropods. In the research field of HIPV, more attention has been paid to the induction of volatiles (Scascighini et al 2005;Maffei et al 2007) than to the relaxation of their production and emission (Fatouros et al 2005). To investigate the effects of genetic variation in parasitoids, fewer tools are available at present.…”