| Fusarium head blight (FHB), caused by Fusarium graminearum is a devastating disease of barley (Hordeum vulgare L.). Resistance in barley to FHB is quantitatively inherited and breeding for resistance is the most viable option to manage this disease. Though several FHB resistance quantitative trait loci (QTL) have been identified, the mechanism(s) of resistance is still unclear. A technology to uncover the mechanisms of resistance to FHB to aid in breeding for resistance is of immediate need for barley breeders.;The metabolites were extracted from mock-inoculated or F. graminearum -inoculated spikelets using aqueous methanol and analyzed using LC-ESI-LTQ-Orbitrap. Data was analyzed through XCMS and CAMERA bioinformatics tools. Compounds were identified based on accurate mass, fragmentation pattern and carbon-isotopic ratio. Thousands of peaks were detected, of which hundreds of treatment significant peaks were selected based on t-tests. These treatment significant metabolites were classified into resistance related constitutive (RRC) or induced (RRI). Barley resists FHB, through jasmonate-signaling and phenylpropanoids. Jasmonate was induced against trichothecene producing but not against the nonproducing isolate, tri5- mutant. All barley genotypes detoxified Deoxynivalenol DON to DON-3-O-glucoside. Potential biomarkers were selected based on their significant abundance, common occurrence and plant defense properties. The potential biomarker metabolites included mainly phenylpropanoids: phenylalanine, p-coumaric acid, cinnamic acid, sinapaldehyde, sinapoyl alcohol, coniferaldehyde, caffeyl aldehyde and coumarin; Flavonoids: catechin and naringenin; fatty acids: jasmonic acid and linolenic acid; resistance indicator (RI) metabolites: total DON produced (TDP) and proportion of DON converted to DON-3-O-glucoside (PDC).;Metabolic profiling was applied to distinguish resistance in barley to FHB. This investigation reports three progressive studies. The first study explored the metabolic phenotyping of resistance in two barley recombinant inbred lines (RIL), H106-4 (resistant) and H106-371 (susceptible) against FHB. This study identified several resistance related (RR) metabolites. The second study was conducted to validate the RR metabolites identified in study-I, and also to identify novel RR metabolites. In study-II, five very resistant two-row genotypes, 'CIho4196', 'Zhedar-1', 'Zhedar-2',' Fredrickson', 'Harbin-2r' and a susceptible CH9520-30 were phenotyped based on metabolic profiling. RR metabolites occurring in more than one genotype were considered potential biomarkers. In study-III, four RILs, two each of black and yellow barley, varying in resistance to FHB were phenotyped for resistance against trichothecene-producing and nonproducing (tri5-) isolates of F. graminearum based on metabolic profiling. |
