Whitebark pine (Pinus albicaulis) disease resistance for conservation

Whitebark pine is listed as endangered in Canada and has been proposed for endangered listing in the U.S. mainly due to the combined impacts of white pine blister rust, mountain pine beetle, fire suppression, and climate change. White pine blister rust represents the most widespread and direct threat to whitebark pine (COSEWIC 2010). In many locations rust infection is present on over 90% of trees and mortality exceeds 50% (Smith et al 2008). Mechanisms of resistance in whitebark pine are variable, and further study is needed to determine the frequency and types of resistance. Complete resistance has been discovered in western white pine and other pines where a hypersensitive response (HR) occurs in the needles (Kinloch et al 2003). Partial resistance refers to all non-HR kinds of resistance and tolerance (needle spots, needle shed, stem symptoms, latency of stem infection, bark reaction, survival with stem infection) (Sniezko et al 2014). No complete resistance (HR) has been detected in whitebark pine so far, but partial resistance has. Screening of seed stock for rust resistance is already occurring at the Dorena Genetic Resource Centre, Coeur D’Alene Nursery, and Kalamalka Forestry Centre, where field collected seed is being grown, seedlings are control inoculated with rust spores, and identification of more rust resistant parent trees is occurring. Results from rust resistance trials can serve to find parents trees from which to collect seed for restoration planting.

In a trial established by Charlie Cartwright, Nicholas Ukrainetz, and Michael Murray (BC Ministry of Forests, Lands, Natural Resource Operations, and Rural Development), whitebark pine seedlings have been planted at Skimikin nursery near Salmon Arm, BC from approximately 500 families and 46 populations across the species range. These families have been split into two series of approximately 250 each. A Ribes garden beside the crop has caused blister rust infection of many of the seedlings through natural inoculation. Because the seedlings of the first series are close to five years old, they are ready for phenotyping for blister rust. Objectives for this study are to i) contribute to early-stage phenotyping efforts to identify more blister rust resistant or tolerant whitebark pine progeny and locations of their parent trees; ii) examine if proximity to Ribes plants affects likelihood of infection by white pine blister rust in a nursery setting; iii) determine the relationships between environmental variables for provenance location and blister rust symptoms.

Funding: Genetic Conservation Technical Advisory Committee (Forest Genetics Council of British Columbia, FLNRORD), UBC Faculty of Forestry, Whitebark Pine Ecosystem Foundation

Principal participants: [ Reid | Aitken ]