Blister rust resistance in whitebark pine (Pinus albicaulis) - early results following artificial inoculation of seedlings from Oregon, Washington, Idaho, Montana, California, and British Columbia seed sources

Abstract

Whitebark pine (Pinus albicaulis) is very susceptible to white pine blister rust, caused by the fungal pathogen Cronartium ribicola. Operational programs to develop resistant populations of whitebark pine are underway. These programs rely on artificial inoculation of young seedlings and can evaluate hundreds of parent trees using seedling progeny in a relatively short time. The trial reported here was undertaken at Dorena Genetic Resource Center (Cottage Grove, Oregon, USA). Inoculation was very effective and produced a high incidence and severity of disease in the seedlings with 99.9 percent of seedlings exhibiting needle spots and averaging more than 125 needle spots per seedling 9 months postinoculation (mpi), and more than 11 stem symptoms per seedling and over 77 percent of seedlings with stem symptoms approximately 15 mpi. Overall, 47 of the 225 families had 100 percent of seedlings with stem symptoms 15 mpi. In this summary, we examine the variation among seed sources in one measure of rust resistance, the percentage of seedlings with early stem infections. The results showed large differences among populations from Oregon, Washington, Idaho, Montana, and California (USA), and British Columbia (Canada). The highest levels of resistance were observed in some seed sources from Oregon and Washington, with some sources showing less than 60 percent stem infection. The two Idaho and Montana seed lots that had been rated moderately rust-resistant in previous testing elsewhere were among the most susceptible in this trial, with 92.4 percent of seedlings with stem symptoms approximately 15 mpi. This was very likely due to lower effective inoculation in the prior test.

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

Sniezko, Richard A.; Kegley, Angelia; Danchok, Robert; Long, Sally. 2018. Blister rust resistance in whitebark pine (Pinus albicaulis) - early results following artificial inoculation of seedlings from Oregon, Washington, Idaho, Montana, California, and British Columbia seed sources. 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. 129-135.