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United States Department of Agriculture

Agricultural Research Service

Research Project: SUSTAINABLE VINEYARD PRODUCTION SYSTEMS

Location: Crops Pathology and Genetics Research

Title: Contrasting Patterns of Genetic Diversity and Population Structure of Armillaria Mellea Sensu Stricto in the Eastern and Western United States

Authors
item BAUMGARTNER, KENDRA
item Travadon, Renaud -
item Bruhn, Johann -
item Bergemann, Sarah -

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 16, 2010
Publication Date: May 1, 2010
Citation: Baumgartner, K., Travadon, R., Bruhn, J., Bergemann, S.E. 2010. CONTRASTING PATTERNS OF GENETIC DIVERSITY AND POPULATION STRUCTURE OF ARMILLARIA MELLEA SENSU STRICTO IN THE EASTERN AND WESTERN UNITED STATES. Phytopathology. 100:708-718.

Interpretive Summary: Armillaria mellea infects over 300 plant species throughout the Northern Hemisphere. Collections from the western US were previously found to be genetically different from those of the eastern US. We compared patterns of genetic differentiation from collections of the pathogen gathered from four locations in the eastern US (N. and S. Appalachians, Ozarks, W. Great Lakes) and four locations in the western US (Berkeley, Los Angeles, St. Helena, and San Jose, CA). A total of 156 strains of the pathogen were genetically characterized with 12 molecular markers known as microsatellite loci. There were no significant genetic differences among eastern and western populations ('ST = -0.002 and 0.004, respectively; P > 0.05), suggesting that the spread of the pathogen’s wind-dispersed spores within each region prevents genetic differentiation. In contrast to the western US, cryptic genetic structure within the eastern US, revealed by Bayesian assignment of multilocus genotypes, suggests that eastern populations are comprised of founder from multiple sources or from a single source with a large effective population size. The existence of shared and unshared loci among eastern and western populations and contrasting patterns of genetic diversity between regions demonstrate that eastern and western A. mellea are two geographically-isolated, divergent genetic pools of isolates.

Technical Abstract: Armillaria mellea infects over 300 hosts in natural and managed ecosystems throughout the Northern Hemisphere. Previously reported nuclear genetic divergenece between eastern and western US isolates is consistent with the disjunct range of A. mellea in N. America, which is restricted mainly to the coasts of the US. We investigated patterns of population structure and genetic diversity of eastern (N. and S. Appalachians, Ozarks, W. Great Lakes) and western US (Berkeley, Los Angeles, St. Helena, and San Jose, CA) populations. A total of 156 diploid isolates were genotyped with 12 microsatellite loci. Absence of geographic differentiation with eastern and western populations ('ST = -0.002 and 0.004, respectively; P > 0.05) suggests that spore dispersal within each region prevents geographic differentiation. In contrast to the western US populations, cryptic genetic structure within the eastern US, revealed by Bayesian assignment of multilocus genotypes, suggests that eastern populations are comprised of founder from multiple sources or from a single source with a large effective population size. The existence of shared and unshared loci among eastern and western populations and contrasting patterns of genetic diversity between regions demonstrate that eastern and western A. mellea are two geographically-isolated, divergent genetic pools of isolates.

Last Modified: 9/10/2014
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