Function of defensive volatiles in pedunculate oak (Quercus robur) is tricked by the moth Tortrix viridana.
The indirect defences of plants are comprised of herbivore-induced plant volatiles (HIPVs) that among other things attract the natural enemies of insects. However, the actual extent of the benefits of HIPV emissions in complex co-evolved plant-herbivore systems is only poorly understood. The observation that a few Quercus robur L. trees constantly tolerated (T-oaks) infestation by a major pest of oaks (Tortrix viridana L.), compared with heavily defoliated trees (susceptible: S-oaks), lead us to a combined biochemical and behavioural study. We used these evidently different phenotypes to analyse whether the resistance of T-oaks to the herbivore was dependent on the amount and scent of HIPVs and/or differences in non-volatile polyphenolic leaf constituents (as quercetin-, kaempferol- and flavonol glycosides). In addition to non-volatile metabolic differences, typically defensive HIPV emissions differed between S-oaks and T-oaks. Female moths were attracted by the blend of HIPVs from S-oaks, showing significantly higher amounts of (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E)-β-ocimene and avoid T-oaks with relative high fraction of the sesquiterpenes α-farnesene and germacrene D. Hence, the strategy of T-oaks exhibiting directly herbivore-repellent HIPV emissions instead of high emissions of predator-attracting HIPVs of the S-oaks appears to be the better mechanism for avoiding defoliation.
Helmholtz Zentrum München, Institute of Biochemical Plant Pathology, Research Unit Environmental Simulation (EUS), 85764 Neuherberg, Germany.
Andrea
A
Ghirardo
Werner
W
Heller
Matthias
M
Fladung
Jörg-Peter
JP
Schnitzler
Hilke
H
Schroeder
D000818:Animals; D002849:Chromatography, Gas; D005247:Feeding Behavior; D005260:Female; D013058:Mass Spectrometry; D009036:Moths / Q000502:physiology*; D029963:Quercus / Q000469:parasitology / Q000502:physiology*; D055549:Volatile Organic Compounds / Q000378:metabolism*
D055549:Volatile Organic Compounds