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Genetic-Geographic Variation in Peridermium harknessii in the North-Central United States. G. A. Tuskan, Assistant professor, Department of Horticulture and Forestry, North Dakota State University, Fargo 58105; J. A. Walla(2), and J. E. Lundquist(3). (2)Research associate, Department of Plant Pathology, North Dakota State University, Fargo 58105; (3)Post-doctoral researcher, Departments of Horticulture and Forestry and Plant Pathology, North Dakota State University, Fargo 58105. Phytopathology 80:857-861. Accepted for publication 26 March 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-857.

Starch gel electrophoresis was used to characterize the amount of isozyme variability found in 201 isolates of Peridermium harknessii collected from 13 disjunct geographic locations and three host species. Significant differences were detected among locations in allozyme frequencies for each of five putative polymorphic isozyme loci. Eight additional isozyme loci were monomorphic. Nei?s FST indicated that 51% of the total variation could be attributed to differences among locations. Cluster analysis, using estimates of genetic distances, grouped locations into two principal clusters. Geographic distribution and stand type appear to have influenced these clusters. Variations in host species did not substantially alter allozyme frequencies. The identification of genetic-geographic variation, in the absence of identified virulence patterns, has implications in selection of inoculum sources in studies of host-pathogen interactions.

Additional keywords: isozyme analysis, Pinus banksiana, Pinus ponderosa, Pinus sylvestris, western gall rust.