Spread of Botrytis cinerea Strains with Multiple Fungicide Resistance in German Horticulture

Abstract

Botrytis cinerea is 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 in Botrytis isolates 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 multiresistant Botrytis strains. 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. cinerea field 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 in B. cinerea populations from different cultures, which presents a major threat to the chemical control of gray mold.

Phenylpyrroles: 30 Years, Two Molecules and (Nearly) No Resistance

“…However, multi-drug resistant (MDR) phenotypes due to increased fungicide efflux affect sensitivity to fludioxonil (Kretschmer et al, 2009). Although MDR does not reach resistance levels sufficient to alter field efficacy of fungicides at their registered field rates, the MDR1h phenotype of B. cinerea group S strains leads to the highest resistance levels to fludioxonil reported for field isolates (Leroch et al, 2013) – besides the specific resistance reported from China (Ren et al, 2016) – and impacts fludioxonil efficacy at least in in vitro assays (Rupp et al, 2016). …”

Evaluation of Host Resistance to Botrytis Bunch Rot in Vitis spp. and Its Correlation with Botrytis Leaf Spot

“…Disease management requires regular applications of fungicides to minimize reductions in yield and quality, in addition to cultural practices, such as canopy thinning. Heavy use of fungicides has contributed to the development of resistance in Botrytis in vineyards around the world (Hahn, 2014;Panebianco et al, 2015;Rupp et al, 2017). Chemical rotation or reducing the number of applications can slow, but not prevent, the development of resistant individuals.…”

When green and red mycology meet: Impressions from an interdisciplinary forum on virulence mechanisms of phyto- and human-pathogenic fungi

“…26 The contribution of alveolar epithelial cells in fungicidal defense was demonstrated by in vitro studies as well as in murine infections, thereby affecting the immunotolerant disposal of inhaled A. fumigatus conidia. Matthias Hahn from the University of Kaiserslautern, Germany, next gave an overview about the spread and fitness of multi-resistant strains of the necrotrophic plant pathogen Botrytis cinerea 27 and described a role of a sensor protein, Sho1, related to BMP1 MAPK signaling 28,29 in pH modulation. Interestingly, sho1 mutants phenocopy the lack of velvet complex components such as Vel1 or Lae1; 30 however, transcriptional profiling studies in planta revealed similarities but also significant differences, leaving the connection between Sho1 and the velvet complex an open issue.…”