Metabolomics to elucidate the mechanisms of resistance in plants against biotic stress

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Resistance in plants against pathogen attack can be complete (vertical or mainly monogenic) or partial (horizontal or mainly polygenic). The latter, because of quantitative inheritance and for lack of suitable tools to screen genotypes, is not well exploited by breeders for biotic stress management. However, the latest developments in metabolomics present a bright future. The mechanisms of true resistance are groped into structural or biochemical. Understanding of plant defense mechanisms at the molecular/metabolic level could lead to novel strategies to manage destructive crop diseases. Metabolomics is an evolving field of systems biology that can shed some light on the functions of genes, and furthermore, metabolites are often the end products of plant defense against stresses, thus it can also be used independently to screen for resistance. Using gas chromatography and mass spectrometry (GC/MS) we have identified more than 200 resistance related (RR) metabolites (higher abundance in resistant than in susceptible). However, GC/MS detects only volatiles and for non-volatile metabolites the use of high accurate mass liquid chromatography and mass spectrometry (LC/MS) is needed. The objective of the present study is to use LC/MS to better understand the mechanisms of resistance in wheat to fusarium head blight (FHB, Fusarium graminearum). In this study a wheat metabolome database will be established. The mechanisms of resistance to invasion will be investigated by metabolic profiling inoculated spikelets of resistant genotypes and multivariate analyses of their abundances to identify RR metabolites. The mechanisms of resistance to spread of pathogen within spike, through degradation of toxin (DON), will be investigated by metabolic profiling of resistant genotypes inoculated with pathogen strains producing and non-producing DON, and through containment of pathogen within rachis nodes based on metabolic profiles of rachis nodes at different growth stages. The knowledgebase generated here on the mechanisms of resistance in wheat to FHB, the biomarker RR metabolites identified, will be exploited to develop a high throughput metabolomics technology for screening wheat breeding lines for resistance to FHB.