Benefits and risks of using fungal toxins in biological control strategies

Fungal pathogens are an enormous source of metabolites, mostly still unknown, differing in chemical structure, biological activity, mechanism of action, specificity. Metabolites from agriculturally important fungi have been intensively studied mainly due to the risks posed to human and animal health when these toxins accumulate in agricultural commodities and are eaten. Thus, the use of fungal metabolites produced by pathogens is thought to pose risks instead of benefits. Often very promising fungal biocontrol agents have been discarded in evaluation because they produce powerful and dangerous toxins in vitro. The evaluation of the risk should be ascertained by considering the global environmental impact, i.e., determining the exact production of those metabolites when fungi are formulated, or when they are applied against, and grown on targets; the toxicity to non-target organisms; their fate in the environment; and the risk of water drift. Conversely, toxins could be used to directly or indirectly enhance the efficacy of biocontrol agents, depending on their biological and chemical characteristics, through: their use as sources of natural pesticides; their syntheses; the selection of better biocontrol agents overproducing toxins; their synergistic use with biocontrol agents; their use as biomarkers. Those aspects are described with particular reference to the metabolites produced by weed fungal pathogens and to the recent results obtained by our research group.