title: The Phytophthora species assemblage and diversity in riparian alder ecosystems of western Oregon, USA.
abstract: Phytophthora species were systematically sampled, isolated, identified and compared for presence in streams, soil and roots of alder (Alnus species) dominated riparian ecosystems in western Oregon. We describe the species assemblage and evaluate Phytophthora diversity associated with alder. We recovered 1250 isolates of 20 Phytophthora species. Only three species were recovered from all substrates (streams, soil, alder roots): P. gonapodyides, the informally described "P. taxon Pgchlamydo", and P. siskiyouensis. P. alni ssp. uniformis along with five other species not previously recovered in Oregon forests are included in the assemblage: P.citricola s.l., P. gregata, P. gallica, P. nicotianae and P. parsiana. Phytophthora species diversity was greatest in downstream riparian locations. There was no significant difference in species diversity comparing soil and unwashed roots (the rhizosphere) to stream water. There was a difference between the predominating species from the rhizosphere compared to stream water. The most numerous species was the informally described "P. taxon Oaksoil", which was mainly recovered from, and most predominant in, stream water. The most common species from riparian forest soils and alder root systems was P. gonapodyides.
authors.affiliation: Oregon State University, Department of Botany and Plant Pathology, Corvallis, Oregon 97330, and University of California, Berkeley, Department of Environmental Science, Policy and Management, Berkeley, California 94704 simslaura@berkeley.edu.
authors.forename: Laura Lee
authors.initials: LL
authors.lastname: Sims
authors.affiliation: Oregon State University, Department of Botany and Plant Pathology, Corvallis, Oregon 97330.
authors.forename: Wendy
authors.initials: W
authors.lastname: Sutton
authors.affiliation: Oregon State University, Department of Botany and Plant Pathology, Corvallis, Oregon 97330.
authors.forename: Paul
authors.initials: P
authors.lastname: Reeser
authors.affiliation: Oregon State University, Department of Botany and Plant Pathology, Corvallis, Oregon 97330.
authors.forename: Everett M
authors.initials: EM
authors.lastname: Hansen
mesh_terms: D029661:Alnus; D017753:Ecosystem; D014644:Genetic Variation; D009922:Oregon; D010838:Phytophthora / Q000145:classification* / Q000235:genetics*; D058441:Rhizosphere; D045483:Rivers; D012988:Soil Microbiology; D014871:Water Microbiology
keywords: ecology; forest pathogens; hardwoods; microorganisms in streams; oomycetes