title: Alternative oxidase reduces the sensitivity of Mycosphaerella graminicola to QOI fungicides.
abstract: Forty-six (1.5%) of nearly 3000 isolates of Mycosphaerella graminicola assayed in vitro were resistant to the QOI fungicide azoxystrobin, but on sub-culturing only ten remained resistant. Cross-resistance extended to other QOIs, but varied between different isolates. In planta the resistant isolates were not well controlled, especially at lower azoxystrobin dose rates. Propyl gallate, an inhibitor of alternative oxidase, potentiated the activity of azoxystrobin in vitro so that resistance was no longer observed. The growth of resistant strains in the presence of azoxystrobin led to alternative oxidase activation. This increased flexibility in respiration allows resistant strains to survive in the presence of a QOI fungicide. Under these conditions, selection for target-site mutations can occur. Using QOIs preventatively reduces the risk of resistance since the alternative oxidase cannot by itself generate all the energy needed for germination and early infection.
authors.affiliation: Department of Environmental Sciences, University Pablo de Olavide, Seville, Spain.
authors.forename: Monica
authors.initials: M
authors.lastname: Miguez
authors.forename: Charlotte
authors.initials: C
authors.lastname: Reeve
authors.forename: Paul M
authors.initials: PM
authors.lastname: Wood
authors.forename: Derek W
authors.initials: DW
authors.lastname: Hollomon
mesh_terms: D000179:Acrylates / Q000633:toxicity*; D001203:Ascomycota / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D019069:Cell Respiration / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D025141:Drug Resistance, Fungal / Q000187:drug effects / Q000502:physiology; D005659:Fungicides, Industrial / Q000633:toxicity*; D008689:Methacrylates; D024101:Mitochondrial Proteins; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D010574:Pesticide Synergists / Q000494:pharmacology; D010940:Plant Proteins; D011435:Propyl Gallate / Q000494:pharmacology; D011743:Pyrimidines / Q000633:toxicity*; D000073739:Strobilurins; D000099188:Alternative Oxidase
chemical_list: D000179:Acrylates; D005659:Fungicides, Industrial; D008689:Methacrylates; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010574:Pesticide Synergists; D010940:Plant Proteins; D011435:Propyl Gallate; D011743:Pyrimidines; D000073739:Strobilurins; D000099188:Alternative Oxidase; C087670:azoxystrobin