Successive cultivation under drought selects for specific microbiome members in the wheat rhizosphere

Growing knowledge on plant microbiomes demonstrates the contribution of the host plant during microbiome assembly, especially under stress conditions commonly threatening crops. To dissect the influence of a plant on its microbiome, repeated cycling of microbiomes can be utilized to enhance functional properties in the enriched microbial communities. We used such a successive cultivation approach for wheat (Triticum aestivum) microbiome under drought conditions and selected lineages for drought resilience and susceptibility, with and without enriching the starting community with a library of bacterial isolates obtained from wheat. Significant differences in the rhizosphere microbiome between selection regimes were confirmed through 16S rRNA gene amplicon sequencing. Notably, replicate lineages of each selection regime showed convergence to similar microbiomes. Specific genera were abundant depending on the selection regimes; Stenotrophomonas under drought resilience, while Rahnella under drought conditions when the strain library was added initially. Applying Stenotrophomonas or Rahnella as single inoculum did not improve drought resilience in wheat. We hypothesize that complex microbiome dynamics take place during successive cultivation, which underscores the importance of considering complex plant-microbiome systems for studying plant stress resilience. Successive cultivation remains a valuable approach for observing rhizosphere microbiome changes under different conditions.