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

ABSTRACT 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. Th...

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Published in:Plant, cell and environment cell and environment, 2012-12, Vol.35 (12), p.2192-2207
Main Authors: GHIRARDO, ANDREA, HELLER, WERNER, FLADUNG, MATTHIAS, SCHNITZLER, JÖRG-PETER, SCHROEDER, HILKE
Format: Article
Language:English
Subjects:
Allelochemicals
Animals
Biological and medical sciences
Chromatography, Gas
Defoliation
Farnesene
Feeding
Feeding Behavior
Female
Flavonols
Forest management
Fundamental and applied biological sciences. Psychology
germacrene
glycosides
herbivore-induced plant volatiles
Herbivores
Infestation
Internet
Leaves
Mass Spectrometry
Moths - physiology
Natural enemies
Pest outbreaks
Pests
PTR-MS
Quercus - parasitology
Quercus - physiology
Quercus robur
Scents
sesquiterpenes
terpenes
Tortrix viridana
Trees
volatile organic compounds
Volatile Organic Compounds - metabolism
Y-tube-olfactometer
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Summary:ABSTRACT 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. This work outlines the biochemical and ecological reasons that some pedunculate oaks (Quercus robur) can tolerate harmful outbreak episodes of the green oak leaf roller (Tortrix viridana), whereas others are heavily defoliated during forest infestations of this pest. Defoliation of oaks is globally a severe problem with multiple consequences for forest management and the cultivation of suitable oak varieties. We performed online analyses of VOCs with PTR‐MS during herbivore feeding experiments and combined them with the results of behavioural experiments with larvae and adult moths. We found conspicuous differences in the VOCs of the two oak phenotypes explaining the preferences of the adult moth for the susceptible phenotype.
ISSN:0140-7791
1365-3040
DOI:10.1111/j.1365-3040.2012.02545.x