White pine blister rust resistance in a seven year old field trial of 28 western white pine (Pinus monticola) families in the Coast Range of Oregon
R. A. SNIEZKO (1), J. Hill (2), R. S. Danchok (2), A. J. Kegley (2), S. Long (2), J. B. Mayo (2), A. J. Smith (3)
(1) USDA FS Dorena Genetic Resource Center, Cottage Grove, OR, U.S.A.; (2) USDA Forest Service/Dorena Genetic Resource Center, Cottage Grove, OR, U.S.A.; (3) Plum Creek Timberlands, Cottage Grove, OR, U.S.A.
Phytopathology 100:S120

Western white pine (WWP) is highly susceptible to the non-native pathogen Cronartium ribicola, cause of white pine blister rust. There are few reports from field trials to verify rust resistance from artificial inoculation programs of WWP. This is the first trial reported for the Coast Range of Oregon. WWP families from two resistance programs were planted in 2003. Families exhibiting several types of resistance, including a hypersensitive reaction (HR) that occurs in the needles, are represented. Infection events had occurred in several years, and both old cankers and recent stem infections were present; however, little mortality has occurred to this point. As of March 2010, 65% of trees were infected, with families ranging from 24 to 100% infected. The number of stem infections per tree ranged from 0 to 91. The susceptible control family had the highest percentage of trees infected and the most severe infections. The families with HR resistance showed relatively high infection, indicating that a strain of the rust virulent to HR in WWP is present, the northernmost documented occurrence of vcr2 to date. Most infections were recent and low in severity at this point. The incidence of rust suggests this site may be a moderate rust hazard and that large differences among families in rust resistance are present. This trial will continue to be monitored to assess the range and durability of blister rust resistance and the growth performance of the families.