Isolation of a Novel Plant Growth‐Promoting <i>Dyella</i> sp. From a Danish Natural Soil

Natural soils are reservoirs of potentially beneficial microbes that can improve plant performance. Here, we isolated 75 bacterial strains from surface-sterilised roots of Arabidopsis thaliana (Arabidopsis) grown in a natural soil derived from an alder swamp. Culture-dependent isolation of individual strains from the roots, followed by monoassociation-based screening, identified seven bacteria that promoted Arabidopsis seedling weight. Of those, we identified a new species from the Dyella genus which increased the biomass of Arabidopsis and tomato seedlings in agar, as well as the shoot biomass of Arabidopsis grown in both the alder swamp soil and potting soil. Dyella sp. A4 specifically promoted the elongation of lateral roots without affecting lateral root number and primary root elongation. The new Dyella sp. A4 expands the toolbox of biostimulants for plant growth promotion via modulating root architecture.