Arthrocnemum macrostachyum y su microbioma como herramienta para la recuperación de suelos degradados

Abstract

In the world, there are problems with contamination of heavy metals and problems about salinity. Both problems affect the quality of soils, the agriculture and, finally, to humans. In this work, Arthrocnemum macrostachyum and its microbiome were used as tool for the phytoremediation of degraded soils. Arthrocnemum macrostachyum is a halophyte plant Cd- hyperaccumulator and hypertolerant and it could be used as phytoremediation tool. This plant grows naturally in Odiel marshes, a polluted ecosystem with high levels of heavy metals. A total of 48 bacteria were isolated (18 from the rhizosphere and 30 endophytes) and all of them could grow in presence of heavy metals and salt. At least one of the PGP properties was present in the isolated bacteria and there were several strains that showed high values of these properties. The heavy metals presence affected to the PGP production by the bacteria both negatively and positively. On the other hand, a high number of isolated bacteria could be new species and they were studied. The results suggest that the isolated bacteria could promote the plant growth even in presence of heavy metals and the set of plant and bacteria could be an interesting tool for the phytoremediation. Two bacterial consortia with the best-performing endophytic (CE) or rhizospheric strains (CR) were selected on basis on the heavy metals resistance and PGP properties. A germination kinetics was observed in presence and absence of heavy metals using both bacterial consortia. On the other hand, a glasshouse experiment was designed to investigate the role of bacterial consortia on its metal uptake capacity and tolerance in plants grown in metal polluted sediments. Plants were assigned to three treatments (with CR, CE and without inoculation). Bacterial inoculation accelerated germination of A. macrostachyum seeds in both the absence and presence of heavy metals. Bioaugmentation with both bacterial consortiums enhanced A. macrostachyum capacity to accumulate ions in its roots. Furthermore, bioaugmentation ameliorated the phytotoxicity levels. Bacteria had a beneficial effect on photochemical apparatus and on the modulation of its oxidative stress machinery. These results suggest that inoculation of A. macrostachyum with the selected bacteria could ameliorate plant establishment and growth in contaminated marshes and improve the metal remediation efficiency. Concernig to the salinity, there is an increasing interest to use halophytes for revegetation of salt affected ecosystems, as well as in understanding their mechanisms of salt tolerance. 8 endophytic bacteria belonging to Bacillus and closely related genera were isolated from phyllosphere of A. macrostachyum growing in salty agricultural soils. The presence of PGP properties and enzymatic activities and tolerance towards NaCl was determined. Effects of inoculation on seeds germination and adult plant growth under experimental NaCl treatments (0, 510 and 1030 mM NaCl) were studied. Inoculation with a consortium including the best performing bacteria improved considerably the kinetics of germination and the final germination percentage of A. macrostachyum seeds. Inoculation of plants mitigated the effects of high salinity on plant growth and physiological performance and, in addition, this consortium appears to have increased the potential of A. macrostachyum to accumulate Na+ in its shoots. Results suggest that bacteria isolated from A. macrostachyum phyllosphere seem to play an important role in plant salt tolerance under stressing salt concentrations, improving seed germination and plant development.