Whitebark pine genecology field trials in British Columbia: Age 5 results

Whitebark pine (Pinus albicaulis Engelm.) is listed as endangered in Canada, chiefly due to decimation by white pine blister rust (WPBR), (caused by the non-native, invasive fungal pathogen Cronartium ribicola J. C. Fisch.), mountain pine beetle (Dendroctonus ponderosae Hopkins) and a shifting climatic niche. In response to the federal listing of the species, it is incumbent on the Province of British Columbia (BC) to take steps towards its restoration. To this end the development of populations of well-adapted parent trees with genetic resistance to WPBR that can provide seed, will be key to BC’s successful regeneration efforts. To select such parental genotypes for the future seedlots that will be needed, multi-environment common garden tests were established in most of the climate types where whitebark pine grows in BC and several farm field settings. Seed sources from across much of the range in Canada and U.S. have been utilized. Age five-years results are reported for blister rust resistance, survival and height growth. Rust incidence at this stage was generally low (0.1–24 %), except for one trial with 95 % of the seedlings infected. Genetic correlation of rust resistance scores across several of the sites were generally non-significant or weak except two northern trials (r = 0.353, p < 0.001). Genetic effects for height growth were uniformly strong for populations, but less so for families within seed source. Population climate was significantly correlated to field performance, particularly on harsher test sites. For example, at McBride Peak correlation of mean annual temperature with height growth was r = −0.514, p = 0.0007. As rust infection increases over time, and test plants grow above the snow, long-term objectives of reliable identification of WPBR resistance parent trees, establishment of climate-based seed transfer guidelines, assessment of variation in rust hazard and trait durability of rust resistance should become evident. Implications for management using rust resistant planting stock in BC are considered.