Effects of Fungicides and Nontarget Pesticides on Accumulation of the Mycotoxin Deoxynivlenol in Wheat.

Deoxynivalenol (DON) is an important virulence factor of the Fusarium head blight of wheat and threatens the health of humans. The effect of fungicides on DON production after stressing wheat to produce H₂O₂ and the effect of nontarget pesticides on DON accumulation are largely unknown. Five pesticides were selected to explore the effect of pesticide-induced oxidative stress on DON production in vitro and in vivo. Epoxiconazole and hexaconazole significantly induced an increase in H₂O₂ in vitro, and H₂O₂ further stimulated the production of DON and the expression of the Tri5 gene. Imidacloprid, isoproturon, and mesosulfuron-methyl had no direct effect in vitro. All pesticides activated the activities of superoxide dismutase, catalase, and peroxidase in wheat and caused the excessive accumulation of H₂O₂. However, excessive H₂O₂ did not stimulate the accumulation of DON. Imidacloprid indirectly stimulated the production of DON in vivo, which may be due to its impact on the secondary metabolism of wheat. In brief, pesticide-induced H₂O₂ in vitro is an important factor in stimulating DON production, but the stressed physiological H₂O₂ in wheat is not sufficient to stimulate DON production. The bioaccumulation results indicated that imidacloprid and epoxiconazole increase the risk of DON contamination, especially under field spraying conditions. [ABSTRACT FROM AUTHOR]