Barley, Hordeum vulgare, has been shown to have broad type-2 resistance to the disease Fusarium Head Blight caused by Fusarium graminearum. The UDP-Glucosyltransferase UGT13248 detoxifies the major F. graminearum mycotoxin Deoxynivalenol (DON) by conversion to the glucoside Deoxynivalenol-3-O-glucoside (D3G). UGT13248 confers type-2 resistance to F. graminearum by limiting fungal spread within the rachis. Wildtype barley plants inoculated with a wildtype strain of F. graminearum, PH1, show similar FHB symptoms as barley plants inoculated with trichothecene-deficient strain of F. graminearum, ∆tri5. Barley plants lacking a functional UGT13248 (H369Y) are highly susceptible to wildtype PH1, but are indistinguishable from wildtype plants when inoculated with a ∆tri5 strain. This suggests that type-2 resistance in barley is dependent on UGT13248 conversion of trichothecenes to their glucoside derivatives.
Various strains of F. graminearum, including PH1, 00-500, 02-15, 06-205, are capable of producing different chemically related trichothecenes: 15-acetyl-deoxynivalenol (15ADON), 3-acetyl-deoxynivalenol (3ADON), Nivalenol (NIV) and NX2, respectively. Previously, it was shown that UGT13248 converts NIV to NIV-3G. Here, we show that UGT13248 converts the remaining mycotoxins to their glucoside derivative. Further, plants lacking UGT13248 function (H369Y) show increased susceptibility to each F. graminearum chemotype. This suggests that UGT13248 confers type-2 resistance to a broad range of F. graminearum chemotypes and their associated mycotoxins. RNA-seq analysis is ongoing and attempts to determine the molecular pathways involved in type-2 resistance in barley. Wildtype barley plants are being compared to H369Y plants at 2, 4, and 6 days post inoculation with F. graminearum.