title: Regional and Temporal Population Structure of Pseudoperonospora cubensis in Michigan and Ontario.
abstract: Cucurbit downy mildew (CDM), caused by the oomycete pathogen Pseudoperonospora cubensis, is a devastating disease that affects cucurbit species worldwide. This obligate, wind-dispersed pathogen does not overwinter in Michigan or other northern regions and new isolates can enter the state throughout the growing season. To evaluate the regional and temporal population structure of P. cubensis, sporangia from CDM lesions were collected from cucurbit foliage grown in Michigan and Ontario field locations in 2011. Population structure and genetic diversity were assessed in 257 isolates using nine simple sequence repeat markers. Genetic diversity was high for isolates from Michigan and Canada (0.6627 and 0.6131, respectively). Five genetic clusters were detected and changes in population structure varied by site and sampling date within a growing season. The Michigan and Canada populations were significantly differentiated, and a unique genetic cluster was detected in Michigan.
authors.affiliation: First, third, and fifth authors: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing; second author: Department of Plant Pathology, North Carolina State University, Raleigh; and fourth author: Canadian Tobacco Research Foundation, Tillonsburg, Ontario, Canada.
authors.forename: R P
authors.initials: RP
authors.lastname: Naegele
authors.affiliation: First, third, and fifth authors: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing; second author: Department of Plant Pathology, North Carolina State University, Raleigh; and fourth author: Canadian Tobacco Research Foundation, Tillonsburg, Ontario, Canada.
authors.forename: L M
authors.initials: LM
authors.lastname: Quesada-Ocampo
authors.affiliation: First, third, and fifth authors: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing; second author: Department of Plant Pathology, North Carolina State University, Raleigh; and fourth author: Canadian Tobacco Research Foundation, Tillonsburg, Ontario, Canada.
authors.forename: J D
authors.initials: JD
authors.lastname: Kurjan
authors.affiliation: First, third, and fifth authors: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing; second author: Department of Plant Pathology, North Carolina State University, Raleigh; and fourth author: Canadian Tobacco Research Foundation, Tillonsburg, Ontario, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Saude
authors.affiliation: First, third, and fifth authors: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing; second author: Department of Plant Pathology, North Carolina State University, Raleigh; and fourth author: Canadian Tobacco Research Foundation, Tillonsburg, Ontario, Canada.
authors.forename: M K
authors.initials: MK
authors.lastname: Hausbeck
mesh_terms: D016000:Cluster Analysis; D019662:Cucurbitaceae / Q000382:microbiology*; D005819:Genetic Markers; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D008824:Michigan; D018895:Microsatellite Repeats / Q000235:genetics; D009864:Ontario; D009868:Oomycetes / Q000235:genetics* / Q000302:isolation & purification; D010935:Plant Diseases / Q000382:microbiology*; D058432:Sporangia
chemical_list: D005819:Genetic Markers