UPLC-ESI-TOF-MS Profiling of Metabolome Alterations in Barley (<i>Hordeum vulgare</i> L.) Leaves Induced by <i>Bipolaris sorokiniana</i>

Spot blotch of barley (<i>Hordeum vulgare</i> L.), caused by <i>Bipolaris sorokiniana</i>, is responsible for major losses in crop yield. Breeding-resistant barley varieties have proven to be an effective countermeasure for protecting agricultural production. Plants react to pathogen attacks by up-regulating secondary metabolites. Marker compounds for a <i>B. sorokiniana</i> infection are examined by untargeted UPLC-TOF-MS metabolomics and lipidomics techniques. Through the analysis of nine quantitatively resistant and susceptible barley genotypes, derived from the nested association mapping population HEB-25, followed by structure identification experiments and spore germination assays, 57 metabolites are identified. In addition to previously known metabolites, the unknown compounds 5-carboxydidehydroblumenol C-9-<i>O</i>-ß-d-glucoside (<b>46</b>) and grasshopper ketone 3-sulfate (<b>47</b>) were elucidated. 5-Carboxyblumenol C-9-<i>O</i>-ß-d-glucoside (<b>45</b>) was described for the first time in barley leaves. Pheophytin derivatives, oxylipins, linolenate-conjugated lipids, and flavone glycosides were described for the first time in connection with infections by phytopathogenic fungi or resistance in barley.