title: Population Structure of Pythium irregulare, P. ultimum, and P. sylvaticum in Forest Nursery Soils of Oregon and Washington.
abstract: Pythium species are important soilborne pathogens occurring in the forest nursery industry of the Pacific Northwest. However, little is known about their genetic diversity or population structure and it is suspected that isolates are moved among forest nurseries on seedling stock and shared field equipment. In order to address these concerns, a total of 115 isolates of three Pythium species (P. irregulare, P. sylvaticum, and P. ultimum) were examined at three forest nurseries using simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers. Analyses revealed distinct patterns of intraspecific variation for the three species. P. sylvaticum exhibited the most diversity, followed by P. irregulare, while substantial clonality was found in P. ultimum. For both P. irregulare and P. sylvaticum, but not P. ultimum, there was evidence for significant variation among nurseries. However, all three species also exhibited at least two distinct lineages not associated with the nursery of origin. Finally, evidence was found that certain lineages and clonal genotypes, including fungicide-resistant isolates, are shared among nurseries, indicating that pathogen movement has occurred.
authors.affiliation: First and sixth authors: U.S. Department of Agriculture-Agriculture Research Service, Horticultural Crops Research Laboratory, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; second, fourth, fifth, and seventh authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74074; and third author: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331.
authors.forename: Jerry E
authors.initials: JE
authors.lastname: Weiland
authors.affiliation: First and sixth authors: U.S. Department of Agriculture-Agriculture Research Service, Horticultural Crops Research Laboratory, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; second, fourth, fifth, and seventh authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74074; and third author: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331.
authors.forename: Patricia
authors.initials: P
authors.lastname: Garrido
authors.affiliation: First and sixth authors: U.S. Department of Agriculture-Agriculture Research Service, Horticultural Crops Research Laboratory, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; second, fourth, fifth, and seventh authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74074; and third author: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331.
authors.forename: Zhian N
authors.initials: ZN
authors.lastname: Kamvar
authors.affiliation: First and sixth authors: U.S. Department of Agriculture-Agriculture Research Service, Horticultural Crops Research Laboratory, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; second, fourth, fifth, and seventh authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74074; and third author: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331.
authors.forename: Andrés S
authors.initials: AS
authors.lastname: Espíndola
authors.affiliation: First and sixth authors: U.S. Department of Agriculture-Agriculture Research Service, Horticultural Crops Research Laboratory, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; second, fourth, fifth, and seventh authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74074; and third author: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Marek
authors.affiliation: First and sixth authors: U.S. Department of Agriculture-Agriculture Research Service, Horticultural Crops Research Laboratory, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; second, fourth, fifth, and seventh authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74074; and third author: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331.
authors.forename: Niklaus J
authors.initials: NJ
authors.lastname: Grünwald
authors.affiliation: First and sixth authors: U.S. Department of Agriculture-Agriculture Research Service, Horticultural Crops Research Laboratory, and Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; second, fourth, fifth, and seventh authors: Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74074; and third author: Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331.
authors.forename: Carla D
authors.initials: CD
authors.lastname: Garzón
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D003710:Demography; D065928:Forests; D005819:Genetic Markers / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D018895:Microsatellite Repeats / Q000235:genetics; D009922:Oregon; D010935:Plant Diseases / Q000382:microbiology; D011110:Polymorphism, Genetic; D011775:Pythium / Q000235:genetics*; D012987:Soil; D014861:Washington
chemical_list: D005819:Genetic Markers; D012987:Soil