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

Tim Birr, Mario Hasler, Joseph-Alexander Verreet and Holger Klink
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Tim Birr: Department of Plant Diseases and Crop Protection, Institute of Phytopathology, Faculty of Agricultural and Nutritional Sciences, Christian-Albrechts-University of Kiel, Hermann-Rodewald-Straße 9, 24118 Kiel, Germany
Mario Hasler: Lehrfach Variationsstatistik, Faculty of Agricultural and Nutritional Sciences, Christian-Albrechts-University of Kiel, Hermann-Rodewald-Straße 9, 24118 Kiel, Germany
Joseph-Alexander Verreet: Department of Plant Diseases and Crop Protection, Institute of Phytopathology, Faculty of Agricultural and Nutritional Sciences, Christian-Albrechts-University of Kiel, Hermann-Rodewald-Straße 9, 24118 Kiel, Germany
Holger Klink: Department of Plant Diseases and Crop Protection, Institute of Phytopathology, Faculty of Agricultural and Nutritional Sciences, Christian-Albrechts-University of Kiel, Hermann-Rodewald-Straße 9, 24118 Kiel, Germany

Agriculture, 2021, vol. 11, issue 3, 1-16

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

Keywords: Zymoseptoria tritici; septoria tritici blotch; wheat; fungicide sensitivity; resistance; EC 50; demethylation inhibitor; succinate dehydrogenase inhibitor; multi-site inhibitor; microtiter assay (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2021
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