Exploring range-wide patterns of genetic resistance to save a species threatened by a non-native disease and climate change

Authors: Jeremy Johnson*, Prescott College/USDA Dorena Genetic Resource Center, Richard A Sniezko, USDA Dorena Genetic Resource Center, Hunter C Mackin, USDA Dorena Genetic Resource Center, Evan Heck, USDA Dorena Genetic Resource Center, Megan Lewien, USDA Dorena Genetic Resource Center, Darren Brons, USDA Dorena Genetic Resource Center, Shannon Mccoy, USDA Dorena Genetic Resource Center, Sara Fraser, USDA Dorena Genetic Resource Center, Angelia Kegley, USDA Dorena Genetic Resource Center, Douglas Savin, USDA Dorena Genetic Resource Center, Gerald FM Page, Oregon State University, Marja Haagsma, Oregon State University, Christopher Still, Oregon State University, Kristen M Waring, Northern Arizona University
Topics: Biogeography
Keywords: Quantitative disease resistance, Major Gene Resistance, White Pine Blister Rust, Five-needle Pine, Quantitative Genetics, Biogeography
Session Type: Paper
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Southwestern white pine (Pinus strobiformis), is a large, long-lived conifer native to the U.S. and Mexico, and is susceptible to white pine blister rust (caused by the non-native fungal pathogen Cronartium ribicola). The species has a major gene, discovered at low frequency in some populations, that conveys complete resistance to the disease but may be overcome in the future by virulent strains of the pathogen. Quantitative disease resistance has also been documented in the species. Even though resistance occurs in southwestern white pine, little is known about the type, frequency, and geographic pattern of resistances across its range. As part of a large collaborative and interdisciplinary study we present early results from a range-wide assessment of 446 families from 104 populations. Seedlings were artificially inoculated with C. ribicola spores and scored for disease symptoms and patterns of growth. All populations show high infection, however, early results indicate that there is a significant (P < 0.05) relationship between the probability of canker development and geographic origin of maternal parent. Moreover, we identified variation in quantitative disease resistance in the species at low frequencies (7%-11%) and have identified several MGR families. By making selections from families with identified resistance we can test their durability, stability, and usability in field trials and these selections can then be used in proactive management of P. strobiformis stands. These results will provide guidance to refine genetic conservation efforts and future seed collections for reforestation and restoration.

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