title: Diversity of Fusarium head blight populations and trichothecene toxin types reveals regional differences in pathogen composition and temporal dynamics.
abstract: Analyses of genetic diversity, trichothecene genotype composition, and population structure were conducted using 4086 Fusarium graminearum isolates collected from wheat in eight Canadian provinces over a three year period between 2005 and 2007. The results revealed substantial regional differences in Fusarium head blight pathogen composition and temporal population dynamics. The 3ADON trichothecene type consistently predominated in Maritime provinces (91%) over the sampled years, and increased significantly (P<0.05) between 2005 and 2007 in western Canada, accounting for 66% of the isolates in Manitoba by the end of the sampling period. In contrast, 3ADON frequency was lower (22%, P<0.001) in the eastern Canadian provinces of Ontario and Québec and did not change significantly between 2005 and 2007, resulting in two distinct longitudinal clines in 3ADON frequency across Canada. Overall, genetic structure was correlated with toxin type, as the endemic population (NA1) was dominated by 15ADON isolates (86%), whereas a second population (NA2) consisted largely of 3ADON isolates (88%). However, the percentage of isolates with trichothecene genotypes that were not predictive of their genetic population assignment (recombinant genotypes) increased from 10% in 2005 to 17% in 2007, indicating that trichothecene type became an increasingly unreliable marker of population identity over time. In addition, there were substantial regional differences in the composition of recombinant genotypes. In western and maritime provinces, NA2 isolates with 15ADON genotypes were significantly more common than NA1 isolates with 3ADON genotypes (P<0.001), and the reverse was true in the eastern provinces of Québec and Ontario. Temporal trends in recombinant genotype composition also varied regionally, as the percentage of 15ADON isolates with NA2 genetic backgrounds increased approximately three fold in western and Maritime provinces, while the opposite trends were observed in Québec and Ontario. The results indicate that F. graminearum population dynamics in Canada have been influenced by a complex adaptive landscape comprising different regional selective pressures, and do not reflect a simple model of dispersal and integration following the introduction of a novel pathogen population. In addition, we identified F. graminearum strains that produce the recently discovered A-trichothecene mycotoxin (NX-2) for the first time in Canada, representing a significant expansion of the known range of NX-2 producing strains in North America.
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, 1815 North University Street, Peoria, IL 61604, USA. Electronic address: amy.kelly@ars.usda.gov.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Kelly
authors.affiliation: 23 Healy Crescent, Winnipeg, Manitoba R2N 2S6, Canada.
authors.forename: Randall M
authors.initials: RM
authors.lastname: Clear
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, 1815 North University Street, Peoria, IL 61604, USA.
authors.forename: Kerry
authors.initials: K
authors.lastname: O'Donnell
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, 1815 North University Street, Peoria, IL 61604, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: McCormick
authors.affiliation: Lacombe Research Centre, Agriculture and Agri-Food Canada, 6000 C and E Trail, Lacombe, Alberta T4L 1W1, Canada.
authors.forename: T Kelly
authors.initials: TK
authors.lastname: Turkington
authors.affiliation: Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, Manitoba R3T 2M9, Canada.
authors.forename: Andy
authors.initials: A
authors.lastname: Tekauz
authors.affiliation: Cereal Research Centre, Agriculture and Agri-Food Canada, 195 Dafoe Road, Winnipeg, Manitoba R3T 2M9, Canada.
authors.forename: Jeannie
authors.initials: J
authors.lastname: Gilbert
authors.affiliation: USDA-ARS, Cereal Disease Laboratory, University of Minnesota, 1551 Lindig Avenue, St. Paul, MN 55108, USA.
authors.forename: H Corby
authors.initials: HC
authors.lastname: Kistler
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, 1815 North University Street, Peoria, IL 61604, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Busman
authors.affiliation: U.S. Department of Agriculture, Agricultural Research Service, 1815 North University Street, Peoria, IL 61604, USA.
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Ward
mesh_terms: D002170:Canada; D005670:Fusarium / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D018598:Minisatellite Repeats; D058885:Multilocus Sequence Typing; D010935:Plant Diseases / Q000382:microbiology*; D011995:Recombination, Genetic; D062211:Spatio-Temporal Analysis; D014255:Trichothecenes / Q000378:metabolism*; D014908:Triticum / Q000382:microbiology*
chemical_list: D014255:Trichothecenes
keywords: 15ADON; 3ADON; Fusarium head blight; NX-2; Population genetics; Trichothecene