Genetic variation of lodgepole pine (Pinus contorta var. Latifolia [Engelm.]) chemical and physical defenses that affect mountain pine beetle Dendroctonus ponderosae attack and tree mortality.

The current outbreak of mountain pine beetle (MPB), Dendroctonus ponderosae (Coleoptera: Curculionidae), and its fungal complex Grosmannia clavigera has affected ~15 million hectares of lodgepole pine Pinus contorta var. latifolia (Engelm.) in British Columbia. This is of great concern to forest industry in British Columbia but it has provided a rare opportunity to study genetic variation of lodgepole pine defense mechanisms against MPB. Based on a previous study, we selected 45 open-pollinated families from a population of 180 families, with the number of trees per family ranging from 16-26 (for a total of 887 trees) from two 20-year field tests which had undergone attack from MPB. Chemical and physical defensive responses were quantified in response to simulated attack by the MPB fungal complex on these 45 families. These responses included: physical exudation of resin, host compartmentalization response to fungal inoculation, and levels of constitutive and induced resin terpenoids. Further assessments were made for tree height, DBH (diameter at breast height ~1.4 m), bark texture, tree mortality, and MPB presence, attack density, reproduction, and brood development, as well as the presence of hypersensitivity reactions by the tree to MPB. --P. iii.