Investigating the potential use of unsaturated fatty acids as antifungal crop protective agents

Abstract

Pathogenic fungi cause significant yield losses and quality reductions to major crops including wheat, canola, and barley. Toxic metabolites produced by some phytopathogenic fungi also pose significant risks to animal and human health. Extensive application of synthetic fungicides is not a sustainable solution since it poses risks to human, animal and environmental health. Unsaturated fatty acids may provide such an alternative because of their possible direct antifungal activity against phytopathogens as well as through the stimulation of plant defense pathways. The present study assessed the in vitro and in vivo efficacy of two hydroxy fatty acids; coriolic acid and ricinoleic acid, against the phytopathogens Fusarium graminearum, Pyrenophora tritici-repentis, Pyrenophora teres f. teres, Sclerotinia sclerotiorum, Leptosphaeria maculans, and Aspergillus niger. Antifungal activity was evaluated using the broth micro-dilution method to determine the minimum inhibitory concentration (MIC). Results indicated that both coriolic acid and ricinoleic acid possessed the strongest inhibitory activity against L. maculans with MIC of 0.73 g/L and 0.83 g/L, respectively, followed by A. niger with MIC of 0.78 g/L for coriolic and MIC of 0.88 g/L for ricinoleic acid. A weaker inhibitory activity of coriolic acid and ricinoleic acid was observed in terms of other fungal pathogens with MICs which varied greatly between species. An antifungal effect was observed for coriolic acid in vivo against pathogenic fungi of wheat and barley. This effect was not correlated to the in vitro activity because ricinoleic acid with equivalent in vitro antifungal activity showed no protective effect in vivo. Moreover, neither coriolic acid nor ricinoleic acid controlled fungal pathogens of canola. In conclusion, coriolic acid inhibits some phytopathogens in vivo and may have the potential to be an effective crop protection agent.