Metabolic profiling of rachis and grain tissues of durum wheat-Thinopyrum germplasm harboring Fhb7E, a major Fusarium Head Blight resistance locus from Th. elongatum

Recent introgression of a major resistance locus, Fhb7E, from the wild Thinopyrum elongatum into bread and durum wheat (DW) showed over 90% decrease of severity of Fusarium Head Blight (FHB) disease. Being effective in different species/backgrounds, Fhb7E offers the way of reaching ample and durable FHB resistance within cultivated germplasm, thus minimizing yield loss and mycotoxin accumulation in grains. Yet, due to the complexity of plant-pathogen interaction and a multigenic host control, understanding of plant strategies against FHB associated with Fhb7E is still incomplete. By using a recombinant DW with a small Th. elongatum chromosome 7E region including Fhb7E on its 7AL arm, we analysed via untargeted metabolomics rachises and grains upon spike inoculation with Fusarium graminearum (Fg) and water. Rachis confirmed to be the key structure where a main metabolic shift occurs differentiating susceptible vs resistant plants. Fhb7E conferred constitutive and early-induced defence response by up-regulating pathways involved in antioxidant activities, cell wall reinforcement and sugar metabolism. Higher accumulation of flavonoids, phenylpropanoids, terpenoids, and peptides in the resistant Fhb7E-carrier line vs control was observed. Fg-induced response also newly highlighted specific importance in Fhb7E-resistance of polyamine biosynthesis, glutathione and vitamin B6 metabolisms, as well as the presence of multiple routes for deoxynivalenol (DON) detoxification. DON was mainly de-epoxidated via conjugation with glutathione, but also largely glycosylated. The results highlight a complex interplay between finely tuned metabolic pathways and specific metabolites at the basis of the outstanding resistance controlled by Fhb7E.