A glutathione S-transferase from Thinopyrum ponticum confers Fhb7 resistance to Fusarium head blight in wheat

Fusarium head blight (FHB), mainly incited by Fusarium graminearum Schwabe, has caused great losses in grain yield and quality of wheat globally. Fhb7, a major gene from 7E chromosome of Thinopyrum ponticum, confers broad resistance to multiple Fusarium species in wheat, and has recently been cloned and identified as encoding a glutathione S-transferase (GST). However, some recent reports raised doubt about if GST is the causal gene of Fhb7. To resolve the discrepancy and validate the gene function of GST in wheat, we phenotyped Fhb7 near-isogenic lines (Jimai22-Fhb7 vs Jimai22) and GST over-expressed lines for FHB resistance. Jimai22-Fhb7 showed significantly higher FHB resistance with a lower percentage of symptomatic spikelets (PSS), Fusarium-damaged kernel (FDK) and Deoxynivalenol (DON) content than susceptible Jimai22 in three experiments. All the positive GST transgenic lines driven by either the maize ubiquitin promoter (MubiP) or its native promoter (NP) with high gene expression in the wheat cultivar ‘Fielder’ showed high FHB resistance. Only one MubiP-driven transgenic line showed low GST expression and similar susceptibility as Fielder, suggesting high GST expression confers Fhb7 resistance to FHB. Knockout of GST in Jimai22-Fhb7 line using CRISPR-Cas9-based gene-editing showed significantly higher FHB susceptibility compared with the non-edited control plants. Therefore, we confirmed GST as the causal gene of Fhb7 for FHB resistance. Considering its major effect on FHB resistance, pyramiding Fhb7 with other QTLs has a great potential to create highly FHB-resistant wheat cultivars.