title: Variable competitive effects of fungicide resistance in field experiments with a plant pathogenic fungus.
abstract: Classic evolutionary theory suggests that mutations associated with antimicrobial and pesticide resistance result in a fitness cost in the absence of the selective antimicrobial agent or pesticide. There is experimental evidence to support fitness costs associated with resistance to anti-microbial compounds and pesticides across many biological disciplines, including human pathology, entomology, plant sciences, and plant pathology. However, researchers have also found examples of neutral and increased fitness associated with resistance, where the effect of a given resistance mutation depends on environmental and biological factors. We used Zymoseptoria tritici, a model evolutionary plant pathogenic fungus, to compare the competitive ability of fungicide-resistant isolates to fungicide-sensitive isolates. We conducted four large-scale inoculated winter wheat experiments at Oregon State University agriculture experiment stations. We found a significant change in the frequency of fungicide resistance over time in all four experiments. The direction and magnitude of these changes, however, differed by experimental location, year of experiment, and inoculum resistance treatment (fungicide-resistant, resistant/sensitive mixture, and fungicide-sensitive). These results suggest that the competitive ability of resistant isolates relative to sensitive isolates varied depending upon environmental conditions, including the initial frequency of resistant individuals in the population.
authors.affiliation: Columbia Basin Agricultural Research Center, Oregon State University, 48037 Tubbs Ranch Road, Adams, OR, 97801, USA.
authors.forename: Christina H
authors.initials: CH
authors.lastname: Hagerty
authors.affiliation: Hermiston Agricultural Research and Extension Center, Oregon State University, 2121 S 1st St, Hermiston, OR, 97838, USA.
authors.forename: Ryan C
authors.initials: RC
authors.lastname: Graebner
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Cordley Hall, 2701 SW Campus Way, Corvallis, OR, 97331, USA.
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Sackett
authors.affiliation: Department of Botany and Plant Pathology, Oregon State University, Cordley Hall, 2701 SW Campus Way, Corvallis, OR, 97331, USA.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Mundt
mesh_terms: D001203:Ascomycota / Q000187:drug effects* / Q000235:genetics; D025141:Drug Resistance, Fungal / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005659:Fungicides, Industrial / Q000494:pharmacology*; D009154:Mutation / Q000235:genetics; D009922:Oregon; D010935:Plant Diseases / Q000382:microbiology*; D014908:Triticum / Q000382:microbiology*
chemical_list: D005656:Fungal Proteins; D005659:Fungicides, Industrial
keywords: 
  Septoria tritici blotch
  ; 
  Zymoseptoria tritici
  ; agriculture; azoxystobin; competitive effects; fitness trade-offs; fungicide resistance; mutation; plant disease