Terpene response of Picea abies and Abies alba to infection with Heterobasidion s.l

The monoterpene composition of Picea abies and Abies alba resin was analysed in relation to growth by Heterobasidion spp. Fifteen-year-old P. abies and A. alba trees were inoculated on branches with three species of Heterobasidion annosum s.l. After 4 months of incubation, each host was colonized to a significantly greater degree by the pathogen specific to that host (H. parviporum on P. abies, H. abietinum on A. alba) than by the other fungi. Analysis of the enantiomeric monoterpene profiles in the spruce and fir showed that the response in terms of the relative proportions of the monoterpene compounds in the resin differed between tree species. Following challenge with Heterobasidion spp., A. alba trees did not show changes in monoterpene composition in addition to those in the wounding response (increase in (-)-alpha-pinene and (-)-camphene, and decrease in beta-phellandrene). In P.abies, (-)-alpha-pinene, (+)-alpha-pinene and delta-3-carene increased following Heterobasidion attack but not after wounding alone.