Rhizosphere symbionts improve water stress tolerance in Moldavian balm through modulation of osmolytes

The metabolomics analysis was used in this study to examine the changes in metabolite profile of Moldavian balm under water-deficit stress, symbiosis with arbuscular mycorrhizal fungus, plant growth-promoting rhizobacteria, and their interactions. This project was realized by applying a completely randomized model considering three factors, the arbuscular mycorrhizal fungus Claroideoglomus etunicatum, the rhizobacteria Micrococcus yunnanensis, and irrigation regimes (100, 70, and 40% field capacity). The results showed that the sugar metabolisms are the most affected metabolic pathways under drought stress. Moreover, the increase of some amino acids, citric acid cycle intermediates, and phenolic acid metabolites could contribute to the tolerance mechanisms of non-inoculated plants against water-deficit stress. These results suggested that soil microorganisms could be used to mitigate the negative impacts of drought stress by inducing the accumulation of some of the intermediary metabolites that act as osmolytes or their precursors. Overall, these results indicated that symbiotic association with soil microorganisms leads to metabolic and physiological adaptation which can increase the performance of this important medicinal plant under drought conditions.