Limber pine (Pinus flexilis) is being threatened by the lethal disease white pine blister rust, expanding bark beetle pressure, and climate change in mountain environments. The treeline ecosystems dominated by limber pine are ecologically valuable for watershed protection and diversity. Consequently, limber pine is of conservation concern in the southern Rocky Mountains.
In a recent publication in the journal Phytopathology, Forest Service researchers report on the first of a series of studies using limber pine families to examine resistance to white pine blister rust and its inheritance in limber pine. Dr. Anna Schoettle and colleagues at USDA Forest Service Dorena Genetic Resources Center report that 14 percent of the 105 tested limber pine families show segregation of a disease-free trait consistent with inheritance by a single dominant gene (i.e., allele), which they name Cr4. The frequency of the Cr4 allele across healthy and recently invaded populations in the southern Rocky Mountains was unexpectedly high (5.0 percent; ranging from 0 to 13.9 percent). The research suggests that Cr4 is not a product of a recent mutation and may have adaptive significance related to other abiotic or biotic stress factors. The identification of Cr4 and other resistance types in native populations of limber pine enables the Forest Service to optimize cost effective treatments by timing interventions to maximize forest health benefits, consistent with the recommendations of the National Strategic Framework for Invasive Species Management.