Effects of plant-selected rhizobacterial communities on the drought resistance of tomato plants

2021 Spring.Includes bibliographical references.Drought stress has had devastating effects for vegetable growers world-wide, leading to much recent research focusing on the development of drought-resilient crops. The importance of the rhizosphere microbiome in plant performance under drought stress is under development, including the use of beneficial inoculations of PGPR and transplanting of microbial communities. However, further research is needed to fully understand plants' innate abilities in mediating rhizobacterial recruitment to benefit plant resistance to drought stress. Here, two greenhouse studies were performed to determine the efficacy of conditioned soils containing plant-selected rhizobacterial communities as a means to increase drought resilience of host plants. Soils were autoclaved to lower microbial complexity and ensure the greatest plant influence over soil rhizobacterial recruitment. Tomato plants were grown in soils, autoclaved and control, to assess microbial recruitment under a gradient of water treatments: well-watered, moderate drought and severe drought. Autoclaved soils revealed a potential amplification of plant-selective influence over microbial community assemblage for drought-specific bacteria. Inoculants derived from this study were used to observe the impacts of microbial history on a plant's ability to tolerate contemporary drought stress conditions. Microbial history was shown to have a significant effect on microbial community composition and plant performance under drought conditions. To further apply the conditioned effects of microbial communities on tomato plants under severe drought stress, a multi-generational study was performed to amplify plant-selected microbial communities from soils previously exposed to severe drought treatment. Effects of soil conditioning and microbial history suggested the presence of bacteria, conditioned over generations of plant-selection, involved in microbially-mediated plant growth restriction of tomatoes as a drought avoidance strategy. In summary, prior exposure of plants and microbial communities to drought stress may provide beneficial traits for host plants under contemporary drought conditions