title: An ephemeral sexual population of Phytophthora infestans in the Northeastern United States and Canada.
abstract: Phytophthora infestans, the causal agent of late blight disease, has been reported in North America since the mid-nineteenth century. In the United States the lack of or very limited sexual reproduction has resulted in largely clonal populations of P. infestans. In 2010 and 2011, but not in 2012 or 2013, 20 rare and diverse genotypes of P. infestans were detected in a region that centered around central New York State. The ratio of A1 to A2 mating types among these genotypes was close to the 50∶50 ratio expected for sexual recombination. These genotypes were diverse at the glucose-6-phosphate isomerase locus, differed in their microsatellite profiles, showed different banding patterns in a restriction fragment length polymorphism assay using a moderately repetitive and highly polymorphic probe (RG57), were polymorphic for four different nuclear genes and differed in their sensitivity to the systemic fungicide mefenoxam. The null hypothesis of linkage equilibrium was not rejected, which suggests the population could be sexual. These new genotypes were monomorphic in their mitochondrial haplotype that was the same as US-22. Through parentage exclusion testing using microsatellite data and sequences of four nuclear genes, recent dominant lineages US-8, US-11, US-23, and US-24 were excluded as possible parents for these genotypes. Further analyses indicated that US-22 could not be eliminated as a possible parent for 14 of the 20 genotypes. We conclude that US-22 could be a parent of some, but not all, of the new genotypes found in 2010 and 2011. There were at least two other parents for this population and the genotypic characteristics of the other parents were identified.
authors.affiliation: School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, United States of America.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Danies
authors.affiliation: School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, United States of America.
authors.forename: Kevin
authors.initials: K
authors.lastname: Myers
authors.affiliation: Department of Biological Sciences, Universidad de los Andes, Bogotá, Colombia.
authors.forename: María F
authors.initials: MF
authors.lastname: Mideros
authors.affiliation: Department of Biological Sciences, Universidad de los Andes, Bogotá, Colombia.
authors.forename: Silvia
authors.initials: S
authors.lastname: Restrepo
authors.affiliation: United States Department of Agriculture - Agriculture Research Services (USDA-ARS), Salinas, California, United States of America.
authors.forename: Frank N
authors.initials: FN
authors.lastname: Martin
authors.affiliation: The James Hutton Institute, Invergowrie, Dundee, United Kingdom.
authors.forename: David E L
authors.initials: DE
authors.lastname: Cooke
authors.affiliation: Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Geneva, New York, United States of America.
authors.forename: Christine D
authors.initials: CD
authors.lastname: Smart
authors.affiliation: Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America.
authors.forename: Jean B
authors.initials: JB
authors.lastname: Ristaino
authors.affiliation: New York State Integrated Pest Management Program, Cornell Cooperative Extension, Geneva, New York, United States of America.
authors.forename: Abby J
authors.initials: AJ
authors.lastname: Seaman
authors.affiliation: Department of Plant Pathology and Environmental Microbiology, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
authors.forename: Beth K
authors.initials: BK
authors.lastname: Gugino
authors.affiliation: Horticultural Crops Research Laboratory, USDA Agricultural Research Service, Corvallis, Oregon, United States of America; Department of Botany & Pant pathology and Center for Genome Biology and Biocomputing, Oregon State University, Corvallis, Oregon, United States of America.
authors.forename: Niklaus J
authors.initials: NJ
authors.lastname: Grünwald
authors.affiliation: School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University, Ithaca, New York, United States of America.
authors.forename: William E
authors.initials: WE
authors.lastname: Fry
mesh_terms: D002170:Canada; D004272:DNA, Mitochondrial / Q000737:chemistry; D005819:Genetic Markers; D005838:Genotype; D006239:Haplotypes; D018895:Microsatellite Repeats; D055750:Phytophthora infestans / Q000235:genetics* / Q000502:physiology; D011156:Population Density; D012098:Reproduction; D014481:United States
chemical_list: D004272:DNA, Mitochondrial; D005819:Genetic Markers