Synthetic rhizosphere community confers drought tolerance in barley

Under current climate change scenarios for temperate ecosystems in Europe, prolonged drought poses a significant threat to barley production necessitating the development of novel strategies to ensure survival under these scenarios. One such approach is to enhance drought resistance through the application of plant-beneficial rhizobacteria. However, studies exploring this strategy for stress mitigation have been limited thus far. To address this, we established a culture collection of rhizosphere bacteria found to be associated with barley hosts under drought stress (drought-tolerant or DT bacteria) and selected a 16-member consortium (drought-tolerant synthetic community/DT-SynCom) based on their relative abundance in the rhizosphere after drought and their in vitro tolerance to osmotic stress. The members of the DT-SynCom include species from Proteobacteria, Firmicutes, and Actinobacteria. Genome analyses revealed the presence of genes associated with plant growth promotion, and in vitro assays confirmed auxin production, ACC deaminase activity, inorganic phosphorus solubilization, and cellulase and chitinase activity in individual consortium members. The DT-SynCom members are non-antagonistic to one another and exhibit either neutral or beneficial effects on barley shoot and root growth in vitro. Pot experiments in three different soil substrates showed that DT-SynCom application reduced the number of wilting leaves and slightly improved barley growth under drought conditions. The results of the research suggest that members of the barley DT-SynCom have beneficial plant traits that result in improved plant growth under drought stress.