Mapped genetic variation of Douglas-fir to guide seed transfer in southwest Oregon

A procedure is illustrated for using mapped genetic variation in indigenous species to develop provisional seed transfer rules and seed zones. Genotypic values for 13 traits of 135 parent trees from 80 locations furnished data for Doulglas-fir in a region in southwest Oregon. Values were estimated from open-pollinated progeny grown in two nursery beds. Two prinicipal components accounted for about 96% of the total family and seed-source variation in all traits. There were strong gradients with location variables: elevation, latitude, distance from the ocean, slope, and sun exposure as affected by shade of adjacent mountains. Seed transfer rules and a procedure for calculating relative risk indicated that risks were large when seed was transferred either east-west along the southern boundary or north-south along the western boundary of the region. These gradients in risk coincide with the steepest precipitation and temperature gradients in the region. Advantages, disadvantages, and potential sources of error in the procedure are discussed. In spite of the limitations of genetic mapping, the conclusion is that for genetically heterogeneous species in mountainous regions, genetic mapping is a prerequisite to directly estimating transfer effects by long-term tests.