The fabrication of fungicides in cost-effective and eco-friendly ways is particularly important for agriculture. Plant pathogenic fungi produce many economic and ecological problems worldwide, which must be controlled with potent fungicides. Here we propose the green synthesis of fungicides, which consist of copper nanoparticles (Cu-NPs) prepared in aqueous media. Through in vitro experiments, the antifungal efficacy against Fusarium solani, Neofusicoccum sp., and Fusarium oxysporum was investigated. Although the antifungal activity differs for each fungal species, it was found that the Cu-NPs induce strong morphological changes in the mycelium. Additionally, the damage of the cell membranes of the pathogens was revealed by microscopic observations. For the three evaluated fungi, fluorescence microscopy demonstrated the intracellular generation of reactive oxygen species in the mycelium. This work proves that the green-synthesized Cu-NPs are potential fungicides against F. solani, Neofusicoccum sp., and F. oxysporum.

During ontogeny, plants interact with a wide variety of microorganisms. The association with mutualistic microbes results in benefits for the plant. By contrast, pathogens may cause a remarkable impairment of plant growth and development. Both types of plant-microbe interactions provoke notable changes in the polyamine (PA) metabolism of the host and/or the microbe, being each interaction a complex and dynamic process. It has been well documented that the levels of free and conjugated PAs undergo profound changes in plant tissues during the interaction with microorganisms. In general, this is correlated with a precise and coordinated regulation of PA biosynthetic and catabolic enzymes. Interestingly, some evidence suggests that the relative importance of these metabolic pathways may depend on the nature of the microorganism, a concept that stems from the fact that these amines mediate the activation of plant defense mechanisms. This effect is mediated mostly through PA oxidation, even though part of the response is activated by non-oxidized PAs. In the last years, a great deal of effort has been devoted to profile plant gene expression following microorganism recognition. In addition, the phenotypes of transgenic and mutant plants in PA metabolism genes have been assessed. In this review, we integrated the current knowledge on this field and analyze the possible roles of these amines during the interaction of plants with microbes.