Bark beetles kill apparently vigorous conifers during epidemics by means of pheromone-mediated aggregation. During non-endemic conditions the beetles are limited to use trees with poor defense, like wind-thrown. To find olfactory cues that help beetles to distinguish between trees with strong or weak defense, we collected volatiles from the bark surface of healthy felled or standing Picea abies trees. Furthermore, living trees were treated with methyl jasmonate in order to induce defense responses. Volatiles were analyzed by combined gas chromatography and electroantennographic detection (GC-EAD) on Ips typographus antennae. Compounds eliciting antennal responses were characterized by single sensillum recording for identification of specific olfactory sensory neurons (OSN). Release of monoterpene hydrocarbons decreased, while oxygenated compounds increased, from spring to early summer in felled trees. In both beetle sexes particular strong EAD activity was elicited by trace amounts of terpene alcohols and ketones. 4-Thujanol gave a very strong response and the absolute configuration of the tested natural product was assigned to be (+)-trans-(1R,4S,5S)-thujanol by stereoselective synthesis and enantioselective gas chromatography. One type of OSN responded to all ketones and five other OSN were characterized by the type of compounds that elicited responses. Three new OSN classes were found. Of the eight EAD-active compounds found in methyl jasmonate-treated bark, the known anti-attractant 1,8-cineole was the one most strongly induced. Our data support the hypothesis that highly active oxygenated host volatiles could serve as positive or negative cues for host selection in I. typographus and in other bark beetles.

Chemical Ecology Department Plant Protection Biology Swedish University of Agricultural Sciences PO Box 102 230 53 Alnarp Sweden

Chemical Ecology Department Plant Protection Biology Swedish University of Agricultural Sciences PO Box 102 230 53 Alnarp Sweden Department Chemistry and Biomedical Sciences Linnaeus University Stuvaregatan 2 392 31 Kalmar Sweden

Chemical Ecology Department Plant Protection Biology Swedish University of Agricultural Sciences PO Box 102 230 53 Alnarp Sweden Faculty of Forestry and Wood Sci Excellent Team for Mitigation Czech University Life Sci Prague Kamycka 129 Prague 6 16521 Suchdol Czech Republic

Department Chemistry and Biomedical Sciences Linnaeus University Stuvaregatan 2 392 31 Kalmar Sweden

Department of Entomology Faculty of Agricultural Sciences and Technology Bahauddin Zakariya University Multan 60800 Pakistan Faculty of Forestry and Wood Sci Excellent Team for Mitigation Czech University Life Sci Prague Kamycka 129 Prague 6 16521 Suchdol Czech Republic

Citace poskytuje Crossref.org