Simbioses de fungos micorrízicos arbusculares e de rizóbio com leguminosas em solo contaminado com arsênio

Abstract

The revegetation of Brazilian soils contaminated with arsenic, in association with the edaphic microbiota, is hampered by lack of information of plant species in association with the As tolerant edaphic microbiota. Therefore, the selection of plant and As tolerant microbial species is the first step for an efficient process of revegetation of the brazilian soils and for the contaminated substrates with this metalloid. Therefore, the objectives of this study were to evaluate the contribution of the arbuscular mycorrhizal fungi (AMF) symbioses and the phytoremediator potential of four leguminous species, associated with rhizobia and characterize and analyze the tolerance of rhizobia isolated from nodules of Stizolobium aterrimum and Crotalaria spectabilis grown in the Au mining area contaminated with high levels of As. Acaulospora morrowieae, Acaulospora sp., Glomus etunicatum and Gigaspora gigantea were inoculated in Acacia magium, Crotalaria juncea, Enterolobium contortisiliquum and Stizolobium aterrimum. These plant species were inoculated with their respective recommended bacterial inoculants. We also evaluated the As tolerance of the N-fixing bacteria isolated from nodules of Crotalaria spectabilis and Stizolobium aterrimum grown in the mining area contaminated with As. The inoculation with AMF enhanced the P:As ratio and reduced the levels of As in the plants reducing the translocation to the shoot. Inoculation with AMF reduced the APX activity in Acacia mangium and Crotalaria juncea, specially, with a phytoprotector effect. The tolerance of bacteria isolated from nodules of Crotalaria spectabilis and Stizolobium aterrimum showed high tolerance to As concentrations (≤ 200 mmol L-1), this tolerance was related to some cultural characteristics such as, fast growth, acidification of the growth culture medium, exopolysaccharide production, and resistance to various antibiotics. We can conclude that the symbioses between legumes and AMF could be used in remediation projects of contaminated areas with As.