Host-Induced Silencing of Fusarium graminearum TRI5 Reduces Fusarium Head Blight and NX Mycotoxin Contamination in Barley

RNA interference (RNAi) technology has been widely used to protect plants from pests and diseases. Fusarium graminearum causes Fusarium head blight (FHB) in wheat and barley, which not only results in grain yield losses, but also threatens food safety due to mycotoxin contamination of grains. F. graminearum trichothecene (TRI) genes are required for trichothecene biosynthesis. Our recent study showed that TRI5 is critical for NX trichothecene production during F. graminearum infection of barley heads. To reduce mycotoxin contamination and disease using RNAi, we generated a hairpin construct targeting the TRI5 gene and introduced it into the NX-producing F. graminearum strain NRRL44211. Compared to 44211, TRI5 RNAi mutants had significantly reduced TRI5 expression and NX toxin production in vitro. Barley heads inoculated with TRI5 RNAi mutants or 44211 showed similar disease levels, however, barley heads inoculated with TRI5 RNAi mutants had significantly reduced NX toxin compared to 44211-inoculated heads. Therefore, a plant RNAi vector targeting the same TRI5 RNAi region was generated and introduced into the barley cv Golden Promise. FHB virulence assays showed that both FHB severity and NX-3 were significantly reduced in TRI5 RNAi transgenic lines compared to controls. Small RNA (sRNA) sequencing of both F. graminearum TRI5 RNAi mutants and barley TRI5 RNAi lines revealed small RNA reads that mapped to the TRI5 sequence, and the sRNA mapping patterns were remarkably similar in Fusarium and barley. Our results indicate that TRI5 can serve as an effective RNAi target to reduce mycotoxin contamination and improve food safety.