The aim of the study was to investigate the impact of drought stress on the metabolite profiles of barley (Hordeum vulgare L.) grain against the background of natural variability depending on growing location and season. Six barley genotypes were field-grown (i) under normal weather conditions at two different sites and (ii) under induced drought conditions, using a Rain-Out-Shelter. Both trials were performed in three consecutive seasons (2010)(2011)(2012). Samples were subjected to a gas chromatography-mass spectrometry metabolite profiling procedure, based on the extraction and fractionation of a broad spectrum of low molecular weight metabolites ranging from lipophilic (e.g. triglyceride-derived fatty acids, free fatty acids, fatty alcohols, sterols) to hydrophilic (e.g. sugars, sugar alcohols, acids, amino acids and amines) compounds. The comparative assessment of the profiling data by means of multivariate analyses revealed that differences in lipophilic metabolites were mainly due to seasonal impact. In contrast water deficit was strongly reflected in quantitative changes of polar metabolites, irrespective of natural variability. The impact factor growing location was differently pronounced depending on the growing season. Univariate statistical analysis revealed 17 metabolites, including the monosaccharides fructose and glucose, the trisaccharide raffinose, several organic acids and the biogenic amine c-aminobutyric acid to be significantly (p-value \ 0.01) influenced by drought stress conditions.

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