Genetic Studies Involving Swiss Needle Cast

Three studies were analyzed this year that examined genetic aspects of Swiss needle cast (SNC) tolerance. Families sampled across the Siuslaw National forest showed differences in foliage health traits, but very little of the variation could be explained by environmental or climatic conditions at the parent tree location. Five test sites of the Nehalem series of progeny trials were measured for DBH. The best families were continuing to have reasonable basal area increments, implying that genetic improvement can produce stock that could offset the 30% volume growth reduction predicted in moderatelyimpacted SNC areas. A third study suggested that Douglas-fir families do not appear to increase 1st-year needle production in response to needle loss and families may differ in the amount of foliage they produce for a given branch diameter. Three genetics studies looking at aspects of tolerance to SNC were completed this year. These studies examined the genetic variation patterns of SNC tolerance over the landscape, the effectiveness of genetically improving tolerance, and whether families differ in their ability to respond to SNC with increased needle production. The first study was supported by SNC Cooperative funding because it was done in conjunction with the early testing study. The second study was funded by the Oregon Department of Forestry and the TRASK metacooperative and the last study was established by the USFS PNW Research Station. Study 1 – Geographic Variation in Swiss Needle Cast Tolerance of Douglas-fir in the Siuslaw National Forest Methods and Materials Genetics of Swiss needle cast (SNC) tolerance and relationships between climatic and geographic variables at parent tree locations and SNC tolerance were investigated in 152 windpollinated Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) families originating from the central coast of Figure 1. Parent tree locations for families studied in the geographic variation study. Newport Lincoln City Neskowin Valley Junction Pleasant Valley