Mostafa Abdelrahman, David J. Burritt, Lam-Son Phan Tran

The sustainable production of food to feed an increasing world population is a major challenge for plant scientists, especially due to the unpredictable and dynamic nature of global climatic conditions. Heat waves, drought, increased soil salinity, unseasonal cold and flooding are all becoming more common climate-related causes of stress for crop plants, and are already affecting yields and the geographical distributions of optimal growing regions for many crops. Therefore, the development and application of multi-faceted strategies, including sustainable agricultural practices and the development and cultivation of intraspecific hybrids containing genetic traits associated with abiotic stress tolerance from wild relatives, will either alone or together be essential to sustainably grow high-yielding crops under increasingly stressful environmental conditions. The development of abiotic stress-resilient crops requires an in-depth knowledge of plant development and of the biological processes that enable plants to survive in stressful environments, and this knowledge can be obtained from "omic" studies, such as bioinformatics, genomics, transcriptomics, proteomics and metabolomics. The plant metabolome can provide a snapshot of the physiological and biochemical status of a plant cell under normal or stressful conditions, and thus it is closely related to the plant phenotypes. Analysis of the metabolomes of plants growing under stressful conditions can be used to identify stress resistance-associated metabolites, or biomarkers, which can then be used by plant breeders as selective markers to help identify the phenotypes, resulted from the complex interactions between genotype and environment, associated with stress-tolerant crop plants. Osmotic adjustment is an important metabolic adaptation mechanism which helps plants survive abiotic stress and can support higher crop yield under stressful environmental conditions. This review highlights the recent advances in our understanding of the functions of abiotic stress-responsive metabolites, with an emphasis on the use of metabolomic quantitative trait locus mapping and osmotic adjustment agronomic traits, for the improvement of crop yields under environmental stresses.