Tebuconazole Reduces Deoxynivalenol Accumulation in Wheat through Activation of Secondary Metabolic Pathways and UDP-Glycosyltransferases

Numerous studies have assessed how fungicides affect the deoxynivalenol (DON) biosynthesis of Fusarium graminearum in vitro. However, little attention has been paid to how fungicide-driven modifications in wheat secondary metabolism regulate DON biosynthesis. This study evaluated the influence of sublethal chiral tebuconazole on DON biosynthesis in vitro and in vivo. In vitro exposure to chiral tebuconazole stimulated DON biosynthesis and upregulated TRI5 and TRI6 gene expression. Conversely, identical treatments substantially lowered DON accumulation in vivo by activating wheat secondary metabolism and UDP-glycosyltransferase (UGT) activity, thereby facilitating the transformation of DON to DON-3-O-glucoside (D3G). Widely targeted metabolomic profiling demonstrated pronounced shifts in the accumulation of endogenous wheat metabolites. Several metabolites, including secoisolariciresinol, kaempferide, harmine, and 4′,7-di-O-methylnaringenin, inhibited DON biosynthesis in vitro and diminished DON accumulation in vivo. These findings provide a novel framework for mitigating DON stimulation under sublethal fungicide exposure and support the development of safer fungicide application practices.