Function of defensive volatiles in pedunculate oak (Quercus robur) in tricked by the moth Tortrix viridana

Ghirardo, Andrea GND; Heller, Werner; Fladung, Matthias GND; Schnitzler, Jörg-Peter; Schröder, Hilke GND

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)- bocimene and avoid T-oaks with relative high fraction of the sesquiterpenes afarnesene 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

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Ghirardo, Andrea / Heller, Werner / Fladung, Matthias / et al: Function of defensive volatiles in pedunculate oak (Quercus robur) in tricked by the moth Tortrix viridana. 2012.

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