Deoxynivalenol in Fusarium graminearum: Evaluation of Cyproconazole Stereoisomers In Vitro and In Planta.

Cyproconazole (CPZ), a representative chiral triazole fungicide, is widely used to control Fusarium head blight (FHB). In this study, the stereoselective efficiency of CPZ was investigated in vitro and in planta. Consistent results were observed between the in vitro bioassay and the in planta visual disease rating, with the control efficacy ordered RS-CPZ > RR-CPZ > SR-CPZ > SS-CPZ. Unexpectedly, the in planta deoxynivalenol level was in the order RR-CPZ > RS-CPZ > SS-CPZ > SR-CPZ, while RS-CPZ inhibited the deoxynivalenol production and ergosterol biosynthesis in Fusarium graminearum. We further investigated that the Tri genes were upregulated in Fusarium graminearum of the RS-CPZ group, and SR-CPZ preferentially degraded in wheat. An extra action mode of CPZ was inferred to stimulate the production of deoxynivalenol. These findings revealed the stereoselective efficiency of CPZ stereoisomers against FHB and provided new insights into the mechanism of action of triazole fungicides against FHB and deoxynivalenol.