Chemical defence in Norway spruce

Sammanfattning: Norway spruce (Picea abies) responds to stress by biosynthesis of chemical substances, which can deter invading insects or pathogens. Some of these substances are volatile and can be emitted to the surroundings while others are accumulated within the tree. Information about the susceptibility of individual plants to infestation, their volatile emissions and chemical defence is of interest, for example, in selecting plants for tree breeding programs.The first part of this research focused on volatiles emitted by Norway spruce plants. Collection of headspace volatiles by SPME and subsequent separation and identification with GC-MS was used to investigate Norway spruce plants of different ages and stress conditions as well as trapping semiochemicals like nepetalactone emitted by the spruce shoot aphids. It was even possible to analyse the emission of single needles in vivo and obtain spatial localisation of the stress reaction to methyl jasmonate or spruce spinning mites. Seedlings of different ages showed differences in chemical composition of emitted volatiles, with the pine weevil repellent, (4S)-(-)-limonene, one of the main compounds. Wounded phloem of conventional plants emitted high amounts of monoterpenes while the phloem of mini plants emitted (3Z)-hexenal and (3Z)-hexen-1-ol. In addition, a method to separate and identify the four diastereomers of nepetalactone by GC-MS and characteristic m/z-fragments was accomplished.The second part of the research deals with the chemical response of Norway spruce roots to inoculation with Heterobasidion annosum. Terpene concentrations increased after inoculation or wounding but the composition was mainly associated with clone identity and not to susceptibility or treatment. In contrast, inoculation with H. annosum induced a treatment-specific alteration of phenol composition. The constitutive phenol composition differed between more and less susceptible clones. The phenols astringin and astringin dimers (piceasides) as well as the terpene ?-longipinene may be suitable markers of low susceptibility for P. abies to Heterobasidion.