Antifungal effect of engineered silver nanoparticles on phytopathogenic and toxigenic Fusarium spp. and their impact on mycotoxin accumulation.

Cereal grains are essential ingredient in food, feed and industrial processing. One of the major causes of cereal spoilage and mycotoxin contamination is the presence of toxigenic Fusarium spp. Nanoparticles have immense applications in agriculture, nutrition, medicine or health but their possible impact on the management of toxigenic fungi and mycotoxins have been very little explored. In this report, the potential of silver nanoparticles (AgNPs) (size 14-100 nm) against the major toxigenic Fusarium spp. affecting crops and their effect on mycotoxin accumulation is evaluated for the first time. The studied Fusarium spp. (and associated mycotoxins) were F. graminearum and F. culmorum (deoxynivalenol, 3-acetyldeoxynivalenol and zearalenone), F. sporotrichioides and F. langsethiae (T-2 and HT-2 toxins), F. poae (nivalenol), F. verticillioides and F. proliferatum (fumonisins B and B) and F. oxysporum (mycotoxins no detected). The factors fungal species, AgNP dose (range 2-45 μg/mL), exposure time (range 2-30 h) and their interactions significantly influence spore viability, lag period and growth rate (GR) in subsequent cultures in maize-based medium (MBM) of all the studied species. The effective lethal doses (ED, ED and ED) to control spore viability and GR were in the range 1->45 μg/mL depending on the remaining factors. At high exposure times (20-30 h), the three effective doses ranged 1-30 μg/mL for all the studied species. At the end of the incubation period (10 days) mycotoxin levels in MBM cultures inoculated with fungal spores from treatments were strongly related with the size reached by the colony at that time. None of the treatments produced stimulation in conidia germination, GR or mycotoxin biosynthesis with respect to controls. Thus, the antifungal effect of the assayed AgNPs against the tested Fusarium spp. suggests that AgNPs could be a new antifungal ingredient in bioactive polymers (paints, films or coating) likely to be implemented in the agro-food sector for controlling these important toxigenic Fusarium spp. and their main associated mycotoxins.