SRP176381 PRJNA512862 Rapid adaptation of Ensifer (Sinorhizobium) meliloti to different host genotypes Mutualism stability is ensured by hosts preferentially associating with higher-quality symbionts, and thus, variation in symbiont quality is expected to erode over time. Yet, variation in symbiont quality is widespread in nature. Here, we experimentally evolved two strains of Ensifer meliloti that differ in their quality, one being low (E. meliloti 1021) and the other high (E. meliloti 1022). We paired these strains with five legume genotypes that differed in their preference for the higher-quality strain, Em1022. At the end of the evolution experiment, which represented just over one year's worth of rhizobia evolution, we sequenced the genomes of rhizobia that evolved with each of the five plant lines (i.e., derived isolates), and compared these genomes to the original isolate used at the beginning of the experiment (i.e., ancestral isolate) to determine what genetic mechanisms govern rhizobial adaptation to different plant lines. Sinorhizobium meliloti