Provenance variation in western white pine (Pinus monticola): The impact of white pine blister rust

Abstract

The five-needle pines have been an important part of the landscape of North America, but they have been severely affected by the introduction of white pine blister rust (causal agent: Cronartium ribicola). However, most of these species have one or more types of some inherent resistance to this exotic disease, such as major gene resistance (complete resistance), and some forms of partial resistance. Longestablished provenance trials in western white pine (WWP, Pinus monticola), established with unselected populations, allow us to investigate and compare genetic variation in our native populations for this resistance. These trials in British Columbia (Canada) and Washington and Idaho (USA) include seed sources that cover all the native range of WWP; the Canadian trials also include some of the selected populations from the ongoing genetic improvement effort. Trends shown here for growth (and survival) are similar to other reports on WWP - a large rather genetically undifferentiated northern population above latitude 45° N and a highly diverse but much less vigorous southern population. But also reported here, after 20 years of cumulative rust infection in the trials, is a trend in this northern population, sometimes significant, showing much higher levels of resistance in the Northern Cascades and lower elevation North Coastal sources compared to interior sources from Idaho and elsewhere. We describe several factors that could have caused these differences, such as natural selection after the early introduction; selection for traits involved in general constitutive defenses, which also gives resistance to this nonnative disease; or refugium differences in the primarily undifferentiated northern population. We also note the high effectiveness of the selection programs and discuss the inherent resistance defenses to this exotic pathogen that exist in native American species of white pine.

Parent Publication

• Proceedings of the IUFRO joint conference: Genetics of five-needle pines, rusts of forest trees, and Strobusphere; 2014 June 15–20; Fort Collins, CO

Citation

King, John N.; DeBell, Jeff; Kegley, Angelia; Sniezko, Richard A.; McDonald, Geral; Ukrainetz, Nicholas. 2018. Provenance variation in western white pine (Pinus monticola): The impact of white pine blister rust. In: Schoettle, Anna W.; Sniezko, Richard A.; Kliejunas, John T., eds. Proceedings of the IUFRO joint conference: Genetics of five-needle pines, rusts of forest trees, and Strobusphere; 2014 June 15-20; Fort Collins, CO. Proc. RMRS-P-76. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 63-80.