GEOGRAPHIC-VARIATION IN SUSCEPTIBILITY OF ALBERTA LODGEPOLE PINE TO WESTERN GALL RUST

Seedlings from 291 open-pollinated families of lodgepole pine (Pinus c ontorta Dougl. ex Loud. var. latifolia Engelm.) from three breeding re gions (B1, B2, and C) in west-central Alberta were evaluated in the gr eenhouse during 1992-1994 for their response to infection by western g all rust (WGR) (Endocronartium harknessii (J.P. Moore) Y. Hiratsuka). Region C is a foothill outlier whereas the two western regions are und er strong cordilleran influence in the Rocky Mountains. Significant va riation in WGR resistance was found among and within regions. A genera l east-west trend was observed, with western and high-elevational fami lies being more susceptible to WGR infection. Regression of WGR resist ance on geographic origins of families accounted for up to 25% of the among-family variation. However, the among-family variation in region C could not be predicted by any geographic variables. Canonical discri minant analysis of WGR resistance and geographic variables could disce rn families in region C from those in regions B1 and B2. While the wid espread introgression from jack pine (Pinus banksiana Lamb.) could con tribute to WGR resistance in lodgepole pine, the observed geographic v ariation could also be a selection gradient induced by regional patter ns of geoclimatic conditions for WGR development.