SYMP 17-2 - Harnessing microbial reactivation in the rhizosphere to support plant resilience

Mitigating the effects of climate-related stress on crops is vital for global food security. The microbiome associated with plant roots, the rhizobiome, can harbor beneficial microbes that alleviate the impacts of stress. However, the drivers of rhizobiome recruitment during periods of stress on the plant and the environment are unclear. We hypothesize that selective activation of dormant bacterial rhizobiome members contributes to the assembly trajectory during and after stress. To address this hypothesis, we performed a greenhouse experiment to assess the active bacterial rhizobiome members' responses to short-term drought within recently planted field soils. By comparing planted and unplanted soils under both droughted and well-watered conditions, we distinguished the active members that were responsive to plant cues from others that were responsive to the immediate changes in the environment that accompanied the drought. We found that drought dynamics of the active rhizobiome were similar across two different crops (a perennial grass, switchgrass, and an annual legume, common bean) but that only the bean rhizobiome exhibited a plant x drought interaction. Thus, the bean plant likely mediates some rhizobiome members' responses to drought, while there was no evidence for this in switchgrass. Furthermore, we identified some bean taxa uniquely activated in the planted drought condition. These results suggest that different crops have different rhizobiome sensitivities to drought and that tailored microbiome management may be needed.