Low soil moisture induces recruitment of Actinobacteria in the rhizosphere of a drought-sensitive and Rhizobiales in a drought-tolerant potato cultivar

Growing evidence suggests that soil microbes can improve plant fitness under drought. However, in potato, the world’s most important non-cereal crop, the role of the rhizosphere microbiome under drought has been poorly studied. Using a cultivation independent metabarcoding approach, we examined the rhizosphere microbiome of two potato cultivars with different drought tolerance as a function of water regime (continuous versus reduced watering) and manipulation of soil microbial diversity (i.e., natural (NSM), vs. disturbed (DSM) soil microbiome). Water regime and soil pre-treatment showed a significant interaction with bacterial community composition of the drought-sensitive (HERBST) but not the drought-resistant cultivar (MONI). Depending on the cultivar, different taxa responded to reduced watering. Under NSM conditions, these were mostly rhizobiales order representative in MONI, and Streptomyces , Glycomyces , Marmoricola , Aeromicrobium , Mycobacterium , amongst Actinobacteriota, and the root endophytic fungus Falciphora in HERBST. Under DSM conditions and reduced watering, Bradyrhizobium , Ammoniphilus , Symbiobacterium and unclassified Hydrogenedensaceae responded in the rhizosphere of MONI compared to the continuous, while in HERBST, fewer taxa of Actinobacteriota and no fungi responded to reduced vs. continuous watering. Overall, our results indicate a strong cultivar specific relationship between potato and their associated rhizosphere microbiomes under reduced soil moisture. ### Competing Interest Statement The authors have declared no competing interest.