Identification of candidate genes responsible for preformed and inducible defence response in oaks against herbivorous insects

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The defoliation of oaks is an urgent problem for forestry in Central Europe. During the last outbreak of the green oak leaf roller (Tortrix viridana) in 2003-2005, we observed fundamental differences in the defoliation level of individual Quercus robur trees in Germany. Some of the trees seem to be somehow “tolerant” (T oaks) against the insects grub while some seem to be conspicuously “susceptible” (S oaks). Within this study we aim to identify the underlying molecular and biochemical mechanisms in oaks responsible for the behavioural preference of Tortrix viridana. By means of combined feeding choice experiments and biochemical analysis of preformed and induced defence mechanisms in T and S oak phenotypes, we will identify the metabolic/chemical basis of the observed differences as prerequisite for the selection of candidate genes expressed in tolerant trees, but not in susceptible ones or vice versa after insects feeding. We will identify functional genes involved in the defence response (i.e. phenolic compounds and plant volatiles) of oak (Q. robur) trees via microarray analysis in already identified T and S oak phenotypes in a research area in North Rhine-Westphalia (Western Germany). This approach will give us a deep insight into the functional genomics of Q. robur relating to the feeding of herbivorous insects. With the identification of molecular and biochemical markers of “Tortrix tolerance” in oaks we can contribute to decision support in sustainable forest management.