The breeding of stress-tolerant cultivated plants that would allow for a reduction in harvest losses and undesirable decrease in quality attributes requires a new quality of knowledge on molecular markers associated with relevant agronomic traits, on quantitative metabolic responses of plants on stress challenges, and on the mechanisms controlling the biosynthesis of these molecules. By combining metabolomics with genomics, transcriptomics and proteomics datasets a more comprehensive knowledge of the composition of crop plants used for food or animal feed is possible. In order to optimize crop trait developments, to enhance crop yields and quality, as well as to guarantee nutritional and health factors, that provides the possibility to create functional food or feedstuffs, the knowledge about the plants' metabolome is crucial. Next to classical metabolomics studies, this review focusses on several metabolomics based working techniques, such as sensomics, lipidomics, hormonomics and phytometabolomics, which were used to characterize metabolome alterations during abiotic and biotic stress, to find resistant food crops with a preferred quality or at least to produce functional food crops are highlighted.Keywords: Plant stress, abiotic stress, biotic stress, metabolomics, phytometabolomics, sensomics, phytohormonics, LC-MS/MS, NMR, targeted metabolomics, untargeted metabolomics, functional food.
Importance of metabolomics for agricultural researchIn their environment plants are often exposed to an enormous number of biotic and abiotic stress factors, such as pathogen and insect infestation as well as extreme temperatures, drought, salinity, pollutants, heavy metals or nutritional deficiencies, that lead to harvest or quality losses, such as the formation of a pronounced bitter off-flavor, and sometimes causes toxicological problems as well as huge global economic losses [1]. The breeding of stress-tolerant cultivated plants that would allow for a reduction in harvest losses and undesirable decrease in quality attributes requires a new quality of knowledge on molecular markers associated with relevant agronomic traits, on quantitative metabolic responses of plants on stress challenges, and on the mechanisms controlling the biosynthesis of these molecules. Thereby, the knowledge of the biologically active metabolites, especially, secondary metabolites as well as metabolic networks of primary and secondary metabolites that were affected upon plant stress conditions are inalienable. For a long time, primary and also secondary metabolites were simply considered as one of the end-products of gene expression and protein activity. Nowadays, it is increasingly accepted that lowmolecular weight molecules modulate macromolecular processes through, e. g. feedback inhibitionand by signaling phytohormons [8]. Therefore, Dixon et al. [8] conclude that, metabolomic studies are "intended to provide an integrated view of the functional status of an organism".Although for a single plant like Arabidosis thaliana no more than ...