title: Genetic analysis and molecular characterisation of laboratory and field mutants of Botryotinia fuckeliana (Botrytis cinerea) resistant to QoI fungicides.
abstract: BACKGROUND
  QoI fungicides, inhibitors of mitochondrial respiration, are considered to be at high risk of resistance development. In several phytopathogenic fungi, resistance is caused by mutations (most frequently G143A) in the mitochondrial cytochrome b (cytb) gene. The genetic and molecular basis of QoI resistance were investigated in laboratory and field mutants of Botryotinia fuckeliana (de Bary) Whetz. exhibiting in vitro reduced sensitivity to trifloxystrobin.
  
  
  RESULTS
  B. fuckeliana mutants highly resistant to trifloxystrobin were obtained in the laboratory by spontaneous mutations in wild-type strains, or from naturally infected plants on a medium amended with 1-3 mg L(-1) trifloxystrobin and 2 mM salicylhydroxamic acid, an inhibitor of alternative oxidase. No point mutations were detected, either in the complete nucleotide sequences of the cytb gene or in those of the aox and Rieske protein genes of laboratory mutants, whereas all field mutants carried the G143A mutation in the mitochondrial cytb gene. QoI resistance was always maternally inherited in ascospore progeny of sexual crosses of field mutants with sensitive reference strains.
  
  
  CONCLUSIONS
  The G143A mutation in cytb gene is confirmed to be responsible for field resistance to QoIs in B. fuckeliana. Maternal inheritance of resistance to QoIs in progeny of sexual crosses confirmed that it is caused by extranuclear genetic determinants. In laboratory mutants the heteroplasmic state of mutated mitochondria could likely hamper the G143A detection, otherwise other gene(s) underlying different mechanisms of resistance could be involved.
authors.affiliation: Department of Environmental and Agro-Forestry Biology and Chemistry, University of Bari, Bari, Italy.
authors.forename: Rita M
authors.initials: RM
authors.lastname: De Miccolis Angelini
authors.forename: Caterina
authors.initials: C
authors.lastname: Rotolo
authors.forename: Mario
authors.initials: M
authors.lastname: Masiello
authors.forename: Stefania
authors.initials: S
authors.lastname: Pollastro
authors.forename: Hideo
authors.initials: H
authors.lastname: Ishii
authors.forename: Francesco
authors.initials: F
authors.lastname: Faretra
mesh_terms: D000085:Acetates / Q000494:pharmacology*; D020171:Botrytis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D045303:Cytochromes b / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D025141:Drug Resistance, Fungal; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005656:Fungal Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D005659:Fungicides, Industrial / Q000494:pharmacology*; D007097:Imines / Q000494:pharmacology*; D008689:Methacrylates / Q000494:pharmacology; D020125:Mutation, Missense; D000073739:Strobilurins; D027843:Vitis / Q000382:microbiology
chemical_list: D000085:Acetates; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D005659:Fungicides, Industrial; D007097:Imines; D008689:Methacrylates; D000073739:Strobilurins; D045303:Cytochromes b; C467051:trifloxystrobin