The EU43 genotype of Phytophthora infestans displays resistance to mandipropamid

• DOI: 10.1111/ppa.13737
• Publication Date: 2023-04-28T12:14:05Z
• Authors: Isaac K. Abuley; James S. Lynott; Jens G. Hansen; David E. L. Cooke; Alison K. Lees
• Keywords: Phytophthora infestans

Abstract Mandipropamid is an active ingredient in the carboxylic acid amide group of fungicides and plays a key role current potato late blight ( Phytophthora infestans ) management programmes. However, reports from Danish growers 2022 suggested that mandipropamid had lost its efficacy. A study was therefore conducted to investigate sensitivity isolates collected fields which been reported be ineffective. Seventy‐two P . Denmark were genotyped using microsatellite markers, revealing dominance clonal lineage EU43 fewer EU41 ‘other’ genetically distinct genotypes. Isolates belonging lineages selected, addition representative clones EU36 EU37 Scotland, tested for at five concentrations ranging 0.1 10 μg/mL on leaf discs (cultivar Maris Piper). The genotype infected all concentrations, no dose–response curve could calculated. dose response observed genotypes EU36, with EC 50 values 0.35 0.75 μg/mL. Field experiments confirmed resistance mandipropamid, significant difference area under disease between untreated treatments. Analysis population showed widely distributed across country. To our best knowledge, this first report