Efficacy and toxic action of the natural product natamycin against Sclerotinia sclerotiorum

Background

Sclerotinia stem rot caused by Sclerotinia sclerotiorum seriously endangers oilseed rape production worldwide, and the occurrence of fungicide resistance mutants of S. sclerotiorum leads to control decline. Thus, it is critical to explore new green substitutes with different action mechanisms and high antifungal activity. Herein, the activity and the action mechanism of natamycin against S. sclerotiorum were evaluated.

Results

Natamycin showed potent inhibition on the mycelial growth of S. sclerotiorum, and the EC₅₀ values against 103 S. sclerotiorum strains ranged from 0.53 to 4.04 μg/mL (mean 1.44 μg/mL). It also exhibited high efficacy against both carbendazim and dimethachlone ‐resistant strains of S. sclerotiorum on detached oilseed rape leaves. No cross‐resistance was detected between natamycin and carbendazim. Natamycin markedly disrupted the hyphal form, sclerotia formation, integrity of cell membrane, and reduced the content of oxalic acid and ergosterol, while increased the reactive oxygen species (ROS) and malondialdehyde content. Interestingly, exogenous addition of ergosterol could reduce the inhibition of natamycin against S. sclerotiorum. Importantly, natamycin significantly inhibited the expression of Cyp51 gene, which is contrary to the results of the triazole fungicide flusilazole, indicating a different action mechanism from triazole fungicides.

Conclusion

Natamycin is a promising effective candidate for the resistance management of S. sclerotiorum.

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