Barrier to Gene Flow Between Eastern and Western Populations of Cronartium ribicola in North America

Abstract

The population structure of Cronartium ribicola from eastern and western North America was studied to test the null hypothesis that populations are panmictic across the continent. Random amplified polymorphic DNA markers previously characterized in eastern populations were mostly fixed in western populations, yielding high levels of genetic differentiation between eastern and western populations (phi(st) = 0.55; theta = 0.36; P < 0.001). An unweighted pair-group method, arithmetic mean dendro-gram based on genetic distances separated the four eastern and four western populations into two distinct clusters along geographic lines. Similarly, a principal component analysis using marker frequency yielded one cluster of eastern populations and a second cluster of western populations. The population from New Mexico was clearly within the western cluster in both analyses, confirming the western origin of this recent introduction. This population was completely fixed (H(j) = 0.000; n = 45) at all loci suggesting a severe recent population bottleneck. Genetic distances were low among populations of western North America (0.00 to 0.02) and among eastern populations (0.00 to 0.02), indicating a very similar genetic composition. In contrast, genetic distances between eastern and western populations were large, and all were significantly different from 0 (0.07 to 0.19; P < 0.001). Indirect estimates of migration were high among western populations, including the number of migrants among pairs of populations (Nm > 1) between New Mexico and British Columbia populations, but were smaller than one migrant per generation between eastern and western populations. These results suggest the presence of a barrier to gene flow between C. ribicola populations from eastern and western North America.

Genetic Resistance to Fusiform Rust in Southern Pines and White Pine Blister Rust in White Pines—A Contrasting Tale of Two Rust Pathosystems—Current Status and Future Prospects

“…Nevertheless, some regional structures are also apparent in both rusts. Eastern and western populations of C. ribicola are strongly differentiated, indicating their different introduction and colonization histories and a barrier to migration [116]. There is also regional differentiation among populations of FR in the southern US and the magnitude of this differentiation was closely associated with geographic distance between populations [75].…”

Microsatellite DNA suggests regional structure in the fusiform rust fungus Cronartium quercuum f. sp fusiforme

“…Furthermore, there is no evidence for genetic variability among population composites representing different regions within either eastern or western areas. Populations in each area are believed to be individual gene pools shaped by founder and migration events that collectively form distinct eastern and western metapopulations that are highly differentiated from each other (Hamelin et al, 2000).…”

An examination of genetic variation and disease spread in Inonotus tomentosus in the sub-boreal spruce zone of British Columbia.

“…has been studied in depth (Hamelin et al 1995a(Hamelin et al , 1995b(Hamelin et al , 2000Hamelin 1996) using random amplified polymorphic DNA (RAPD) markers and isoenzyme patterns in C. ribicola.…”

“…The resulting amplification products are separated by gel electrophoresis and reveal banding patterns unique to each isolate. This technique has been used in studies of fungal plant pathogens and has provided a suitable estimation of intraspecific genetic variation in fungal populations on a small scale (Hamelin et al 2000;Gogglioli et al 1998;Printzen et al 1999). RAPDs have a number of advantages that make them desirable for population genetic analysis.…”