The relationship between features enabling SDHI fungicide binding to the Sc-Sdh complex and its inhibitory activity against Sclerotinia sclerotiorum.

BACKGROUND: A new generation of succinate dehydrogenase inhibitors (SDHIs) with high efficiency and broad-spectrum antifungal activity has been frequently used in crop production. Sclerotinia stem rot is a major disease of various plants and crops caused by Sclerotinia sclerotiorum. Although benzovindiflupyr and isopyrazam reportedly have high activity against S. sclerotiorum, little is known about the bioactivity of different SDHIs classes against S. sclerotiorum or the mechanism of their differential antifungal activity. RESULTS: The in vitro tests revealed that the pyrazole-4-carboxamides of SDHIs (benzovindiflupyr, isopyrazam, fluxapyroxad, pydiflumetofen) had the highest activity against S. sclerotiorum followed by pyridine carboxamides (boscalid), pyridinyl-ethyl benzamides (fluopyram) and thiazole carboxamides (thifluzamide), among them thifluzamide showed poor antifungal activity with EC50 values over than 6.01 mg L(-1) . The pyrazole-4-carboxamides of SDHIs showed both satisfactory protective and curative activity against Sclerotinia stem rot. After treated with the pyrazole-4-carboxamides of SDHIs, mitochondrial function in S. sclerotiorum decreased obviously. The enzyme activity assays revealed a lower affinity between thifluzamide and the Sc-Sdh complex than was observed for the other six fungicides, with IC50 values ranging from 0.0036 to 1.2088 mumol L(-1) . Additionally, the docking positions of fungicides were similar, yet binding energies were differed in the docking study with the Sdh complex. The correspondingly weaker hydrogen bonds may be responsible for the poor activity of thifluzamide against S. sclerotiorum. CONCLUSION: Understanding different binding features of various SDHIs classes with the Sc-Sdh complex might be beneficial for the design and development of highly effective broad-spectrum fungicides to ensure high yield and quality in crops by reducing fungicide use. This article is protected by copyright. All rights reserved.