Deciphering the role of plant growth-promoting rhizobacteria in the tolerance of the invasive cordgrass Spartina densiflora to physicochemical properties of salt-marsh soils

A glasshouse experiment was conceived to assess the role of a bacterial consortium (Pseudomonas composti SDT3, Aeromonasaquariorum SDT 13 and Bacillus sp. SDT14) isolated from the rizhosphere of S. densiflora on its growth and physiological tolerance to the physicochemical properties of marsh soils. Two inoculation treatments (with and without inoculation) in combination with two soil types (from Piedras and Odiel marshes, SW Spain) were assigned for 50 days. Growth parameters, combined with measurements of gas exchange, efficiency of PSII biochemistry, photosynthetic pigments and leaf water content were measured. In addition, the accumulation of nutrients and trace elements were determined. The inoculation improved growth of S. densiflora through a beneficial effect on its photochemical apparatus due to its impact on chlorophyll concentration. This enhancement happened under both soil conditions and was mainly reflected in a greater length and diameter of roots. Also, inoculation favoured leaf water content through the decline in stomatal conductance and increment in root-to-shoot ratio. Moreover, this consortium was able to stimulate ion accumulation in roots and leaves. Selected rhizospheric bacteria appear to play a significant role in S. densiflora growth response and tolerance to the physicochemical properties of marshes soils.