Effects of double-stranded RNAs targeting Fusarium graminearum TRI6 on Fusarium head blight and mycotoxins.

Fusarium graminearum is the causal agent of Fusarium head blight (FHB), which reduces crop yield and contaminates grains with poisonous trichothecene mycotoxins, including deoxynivalenol (DON). DON functions as an important virulence factor that promotes FHB spread in wheat; therefore, reducing DON production will decrease yield losses to FHB and enhance food safety. Recent progress using topical application of double-stranded (dsRNA) to reduce F. graminearum infection has provided encouraging results. In this study, we designed and synthesized dsRNA targeting the transcription factor TRI6 (TRI6-dsRNA), which is a key regulator of DON biosynthesis. The expression of F. graminearum TRI6 was significantly reduced in detached wheat heads treated with TRI6-dsRNA solution compared to water-treated controls. Furthermore, TRI6-dsRNA treatments reduced disease and DON accumulation in inoculated detached wheat heads. Therefore, topical applications of TRI6-dsRNA on wheat heads of intact plants were assessed for their ability to reduce FHB and DON under growth chamber and greenhouse conditions. When wheat heads were treated with TRI6-dsRNA solution in growth chamber condition, TRI6-dsRNA treatments failed to prevent FHB spread. However, when wheat heads were treated with TRI6-dsRNA solution under the greenhouse condition, FHB and DON were significantly reduced, and infection was restricted to the inoculated floret. In addition, addition of TRI6-dsRNA to toxin-induction liquid media had no effect on F. graminearum DON production. Our study demonstrates that the efficacy of dsRNA applications is strongly dependent on application methods and environmental conditions.