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White Pine Blister Rust Resistance in Limber Pine: Evidence for a Major Gene

February 2014 , Volume 104 , Number  2
Pages  163 - 173

A. W. Schoettle, R. A. Sniezko, A. Kegley, and K. S. Burns

First author: United States Department of Agriculture (USDA), Forest Service, Rocky Mountain Research Station, Fort Collins, CO 80526; second and third authors: USDA Forest Service, Dorena Genetic Resource Center, Cottage Grove, OR 97424; and fourth author: USDA Forest Service, Forest Health Protection, Golden, CO 80401.

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Accepted for publication 2 August 2013.

Limber pine (Pinus flexilis) is being threatened by the lethal disease white pine blister rust caused by the non-native pathogen Cronartium ribicola. The types and frequencies of genetic resistance to the rust will likely determine the potential success of restoration or proactive measures. These first extensive inoculation trials using individual tree seed collections from >100 limber pine trees confirm that genetic segregation of a stem symptom-free trait to blister rust is consistent with inheritance by a single dominant resistance (R) gene, and the resistance allele appears to be distinct from the R allele in western white pine. Following previous conventions, we are naming the R gene for limber pine “Cr4.” The frequency of the Cr4 allele across healthy and recently invaded populations in the Southern Rocky Mountains was unexpectedly high (5.0%, ranging from 0 to 13.9%). Cr4 is in equilibrium, suggesting that it is not a product of a recent mutation and may have other adaptive significance within the species, possibly related to other abiotic or biotic stress factors. The identification of Cr4 in native populations of limber pine early in the invasion progress in this region provides useful information for predicting near-term impacts and structuring long-term management strategies.

This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2014.