Copper nanoparticles against benzimidazole-resistant Monilinia fructicola field isolates

Nano-fungicides are expected to play an important role in future plant disease management. Their unique properties include a broad antimicrobial action, increased effectiveness in lower doses, slower a.i. release and/or enhanced drug delivery and an ability to control drug-resistant pathogens, which makes them appealing candidates for use as eco-friendly antifungal alternatives to counter fungicides resistance. Copper nanoparticles (Cu-NPs) could suppress mycelial growth in both sensitive (BENS) and resistant (BEN-R) Monilinia fructicola isolates harboring the E198A benzimidazole resistance mutation, more effectively than copper oxide NPs (CuO-NPs) and Cu(OH)₂. A significant synergy of Cu-NPs with thiophanate methyl (TM) was observed against BEN-S isolates both in vitro and when applied on plum fruit suggesting enhanced availability or nanoparticle induced transformation of TM to carbendazim. ATP-dependent metabolism is probably involved in the mode of fungitoxic action of Cu-NPs as indicated by the synergy observed between Cu-NPs and the oxidative phosphorylation-uncoupler fluazinam (FM). Copper ion release contributed in the toxic action of Cu-NPs against M. fructicola, as indicated by synergism experiments with ethylenediaminetetraacetic acid (EDTA), although the lack of correlation between nano and bulk/ionic copper forms indicate an additional nano-property mediated mechanism of fungitoxic action. Results suggested that Cu-NPs can be effectively used in future plant disease management as eco-friendly antifungal alternatives to counter fungicides resistance and reduce the environmental footprint of synthetic fungicides.