Broad environmental tolerance of native root-nodule bacteria of Biserrula pelecinus indicate potential for soil fertility restoration

Abstract

Background: Biserrula pelecinus is an annual legume native to the Mediterranean basin, found in pastureland, alone or in association with other legumes (Leguminosae) and grasses (Poaceae). It has been used in revegetation programmes of mining wastes showing phytoremediation potentials and thus becoming potentially highly attractive for plant ecology and restoration management of natural ecosystems.

Aims: To characterise native root-nodule bacteria isolated from B. pelecinus from the Iberian Peninsula, and to select suitable N fixers for field-application and soil rehabilitation.

Methods: Strains were isolated and molecularly identified by 16S rRNA amplification and sequencing. Strains were phenotypically characterised in different abiotic conditions (acidity, salinity and heavy metals) and tested for their ability to fix atmospheric N₂. The most suitable N fixers were applied in greenhouse experiments with B. pelecinus under different fertilization levels to assess their tolerance to fertilized and polluted soils, commonly encountered in restoration projects.

Results: B. pelecinus root-nodule isolates tolerated pH from 4.5 to 9.5 grew in saline conditions (2.5% of NaCl), and tolerated 50 µM of Al³⁺ and Mn²⁺. Three isolates efficient in N₂ fixation, relative to the reference Mesorhizobium strain, were considered excellent candidates for the amelioration of nutrient poor sites.

Conclusions: These results provide valuable information for the potential use in soil restoration of B. pelecinus in a wide-range of conditions, exploiting the natural variability of its root-nodule bacteria.

Keywords:

• acidity
• Biserrula pelecinus
• biological nitrogen fixation
• fertilization
• heavy metals
• salinity

Acknowledgements

This work was supported by the doctoral research grant (SFRH/BD/17252/2004) from the Portuguese Foundation for Science and Technology (FCT).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by The Portuguese Foundation for Science and Technology (FCT) [SFRH/BD/17252/2004].

Notes on contributors

Cláudia S. L. Vicente

Cláudia Vicente’s main research interests are related to environmental microbiology, mostly the characterisation of microbial communities associated with agricultural and forest soils, and research on their biotechnological potential.

María A. Pérez-Fernández

María Pérez-Fernández’s main research interests include plant–soil–microorganisms interactions in forests along altitudinal and latitudinal gradients, evaluating the effect of climate change in the dynamics of the soil microorganisms, their activities and how they modulate tree establishment and putative changes in the tree-line.