Terpenoid metabolite profiling in Sitka spruce identifies association of dehydroabietic acid, (+)-3-carene, and terpinolene with resistance against white pine weevil

The white pine weevil (Pissodes strobi Peck) is an important insect pest in the Pacific Northwest that attacks the apical stem leaders of spruce (Picea spp.) causing damage to tree form, growth, and stand development. Because of attacks by weevils, Sitka spruce (P. sitchensis Bong.) is not commonly replanted as a commercial species in coastal British Columbia, despite its economic and ecological importance. In the last decade, the focus of research on Sitka spruce resistance against weevils has moved from silvicultural approaches to breeding for resistance. The British Columbia Ministry of Forests and Range, in collaboration with the Canadian Forest Service, has developed a successful program to screen populations and select tree genotypes for resistance to weevil attack. Part of this effort has been the establishment of clonebanks that contain genotypes from throughout the range of Sitka spruce. For metabolite profiling, using gas chromatography coupled with flame ionization detection or mass spectrometry, we analysed 111 different genotypes to determine the relationship of mono- and di-terpenoid oleoresin compounds with the resistance rating. Dehydroabietic acid, a diterpene, was identified as a strong indicator of resistance. Two monoterpenes, (+)-3-carene and terpinolene, were also associated with resistance in genotypes originating from one of the areas (Haney) in which resistance has been noted.