Temporal Changes in Sensitivity of Zymoseptoria tritici Field Populations to Different Fungicidal Modes of Action

Septoria tritici blotch (STB; Zymoseptoria tritici), one of the most important foliar diseases in wheat, is mainly controlled by intensive use fungicides during crop growth. Unfortunately, Z. field populations have developed various extents resistance to different groups fungicides. Due complete quinone outside inhibitors (QoIs), fungicidal control STB relies on demethylation (DMIs) and succinate dehydrogenase (SDHIs) as well multi-site inhibitors. In this study, temporal changes sensitivity selected DMIs (tebuconazole, propiconazole, prothioconazole, prochloraz), SDHIs (boscalid, bixafen), (chlorothalonil, folpet) were determined microtiter assays using isolated 1999, 2009, 2014, 2020 a high-disease-pressure high-fungicide-input area Northern Germany. For four tested DMI fungicides, significant shift towards decreasing was observed between 1999 whereby concentrations inhibiting fungal growth 50% (EC50) increased differentially DMIs. Since EC50 values tebuconazole, prochloraz remain stable, whereas for prothioconazole slightly found. A also both SDHI contrast DMIs, boscalid bixafen continuously 2020, but increasing much smaller compared those No chlorothalonil folpet over last 21 years. The adaptation single-site (DMIs, SDHIs) used represents major challenge future wheat cultivation.