title: Spread ofBotrytis cinereaStrains with Multiple Fungicide Resistance in German Horticulture.
abstract: Botrytis cinereais a major plant pathogen, causing gray mold rot in a variety of cultures. Repeated fungicide applications are common but have resulted in the development of fungal populations with resistance to one or more fungicides. In this study, we have monitored fungicide resistance frequencies and the occurrence of multiple resistance inBotrytisisolates from raspberries, strawberries, grapes, stone fruits and ornamental flowers in Germany in 2010 to 2015. High frequencies of resistance to all classes of botryticides was common in all cultures, and isolates with multiple fungicide resistance represented a major part of the populations. A monitoring in a raspberry field over six seasons revealed a continuous increase in resistance frequencies and the emergence of multiresistantBotrytisstrains. In a cherry orchard and a vineyard, evidence of the immigration of multiresistant strains from the outside was obtained. Inoculation experiments with fungicide-treated leaves in the laboratory and with strawberry plants cultivated in the greenhouse or outdoors revealed a nearly complete loss of fungicide efficacy against multiresistant strains.B. cinereafield strains carrying multiple resistance mutations against all classes of site-specific fungicides were found to show similar fitness as sensitive field strains under laboratory conditions, based on their vegetative growth, reproduction, stress resistance, virulence and competitiveness in mixed infection experiments. Our data indicate an alarming increase in the occurrence of multiresistance inB. cinereapopulations from different cultures, which presents a major threat to the chemical control of gray mold.
authors.affiliation: Department of Biology, University of Kaiserslautern Kaiserslautern, Germany.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Rupp
authors.affiliation: Esteburg Fruit Research and Advisory CentreJork, Germany; Department of Food Science, Aarhus UniversityÅrslev, Denmark.
authors.forename: Roland W S
authors.initials: RW
authors.lastname: Weber
authors.affiliation: Belchim Crop Protection Burgdorf, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rieger
authors.affiliation: NüPA GmbH Karlsruhe, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Detzel
authors.affiliation: Department of Biology, University of Kaiserslautern Kaiserslautern, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Hahn
keywords: Botrytis cinerea; Germany; fitness; fungicide resistance; multiple resistance; ornamental flowers; raspberry; strawberry