Herbivore-Mediated Effects of Glucosinolates on Different Natural Enemies of a Specialist Aphid

Abstract

The cabbage aphid Brevicoryne brassicae is a specialist herbivore that sequesters glucosinolates from its host plant as a defense against its predators. It is unknown to what extent parasitoids are affected by this sequestration. We investigated herbivore-mediated effects of glucosinolates on the parasitoid wasp Diaeretiella rapae and the predator Episyrphus balteatus. We reared B. brassicae on three ecotypes of Arabidopsis thaliana that differ in glucosinolate content and on one genetically transformed line with modified concentrations of aliphatic glucosinolates. We tested aphid performance and the performance and behavior of both natural enemies. We correlated this with phloem and aphid glucosinolate concentrations and emission of volatiles. Brevicoryne brassicae performance correlated positively with concentrations of both aliphatic and indole glucosinolates in the phloem. Aphids selectively sequestered glucosinolates. Glucosinolate concentration in B. brassicae correlated negatively with performance of the predator, but positively with performance of the parasitoid, possibly because the aphids with the highest glucosinolate concentrations had a higher body weight. Both natural enemies showed a positive performance-preference correlation. The predator preferred the ecotype with the lowest emission of volatile glucosinolate breakdown products in each test combination, whereas the parasitoid wasp preferred the A. thaliana ecotype with the highest emission of these volatiles. The study shows that there are differential herbivore-mediated effects of glucosinolates on a predator and a parasitoid of a specialist aphid that selectively sequesters glucosinolates from its host plant.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-012-0065-2) contains supplementary material, which is available to authorized users.

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“…Interestingly, D. semiclausum showed a reversed preference to the host-infested plants at higher aphid density (Chapter 5). A positive correlation between preference behaviour and performance of parasitoids has been reported previously Kos et al, 2012). In this thesis, we also found that the parasitoid D. semiclausum preferred volatiles from plants that benefit their performance.…”

Characterization of RsMYB28 and RsMYB29 transcription factor genes in radish (Raphanus sativus L.)

“…Glucosinolates (GSLs) are amino acid-derived natural plant products in the Brassicaceae family, which are well known for their role as a degradation product that induces resistance against generalist herbivores (Kos et al, 2012) and microorganisms (Brader et al, 2006) in plants, as well as for their cancer-preventing properties in humans. In addition, GSLs have gained increasing significance as flavor compounds and potential biopesticides (Mithen et al, 2003).…”

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