Mercaptoimidazole-capped gold nanoparticles as a potent agent against plant pathogenic fungi

Plant pathogenic fungi pose a substantial challenge to agricultural production, but the conventional fungicide-based approaches are losing importance. As agents with broad-spectrum antibacterial effects, gold nanoparticles (Au NPs) are found to have antifungal effects; however, no study has examined their application in agriculture as fungicides. Accordingly, this study investigates the activity of 2-mercaptoimidazole-capped Au NPs (MI-Au NPs) against the ‘top’ plant pathogenic fungi, finding that they could inhibit Magnaporthe oryzae, Botrytis cinerea, Fusarium pseudograminearum and Colletotrichum destructivum by inducing cytoplasmic leakage. Moreover, MI-Au NPs are found to protect plants from infection by B. cinerea. Specifically, pot experiments demonstrate that MI-Au NPs decrease the incidence rate of B. cinerea infection in Arabidopsis thaliana from 74.6% to 6.2% and in Solanum lycopersicum from 100% to 10.9%, outperforming those achieved by imazalil. Furthermore, the biosafety assays reveal that MI-Au NPs cannot penetrate the cuticle of plant cells or negatively influence plant growth, and it is safe to mammalian cells. In summary, the findings of this study will support the development of NP-based antifungal agents for use in agriculture.