ABSTRACT: Areas affected by coal mining can be recovered by revegetation with leguminous plants associated with nitrogen-fixing bacteria. This study addressed the isolation and characterization of native nitrogen-fixing bacteria from coalmine wasteland under different vegetation restoration approaches using Macroptilium atropurpureum (DC) Urb and Vicia sativa L. as trap plants. The bacteria were characterized and identified on the basis of 16S rRNA sequences. Additionally, nitrogen-fixing strains were characterized for tolerance to high heavy metal and low pH levels, as well as for their effect on growth, nodulation, and symbiotic efficiency of M. atropurpureum and V. sativa. Soil samples were taken from the rhizosphere of eight areas, between 6 and 20 years under vegetation restoration, in the coal mining area of Candiota, RS-Brazil. The following properties were evaluated: colony characterization on solid “79” culture medium; pH (3.0-9.0) and heavy metal (Cr, Cd, Zn, Cu, and Ni) tolerance; partial sequencing of 16S rRNA gene; presence of nodA and nifH genes and symbiotic efficiency. A total of 115 isolates, i.e., 77 from M. atropurpureum and 38 from V. sativa, were obtained. The tolerance of these isolates is high for a wide range of pH levels and heavy metal contents, and 18 among them were selected for symbiotic efficiency and 16S rRNA sequencing. Inoculated with M. atropurpureum, the strains UFSM-B53, UFSM-B64, and UFSM-B74 had high symbiotic efficiency. The nitrogen-fixing bacteria were classified in the genera Rhizobium, Bradyrhizobium, and Burkholderia. The results indicate the potential of these native rhizospheric bacterial strains as inoculants and biofertilizers for legume species under pH and heavy metal stress in coal mining degraded areas in Southern Brazil.

RESUMO No estado do Rio Grande do Sul, os reflorestamentos de eucalipto encontram-se, geralmente, em solos de baixa fertilidade natural, favorecendo a associação ectomicorrízica. Neste trabalho, avaliou-se o efeito da inoculação dos isolados de fungos ectomicorrízicos UFSC-Pt116, UFSC-Pt188 e UFSC-SA9, sobre plantas de Eucalyptus grandis, em Neossolo Quartzarênico. As avaliações foram realizadas aos 30, 45, 60, 75 e 90 dias após semeadura. Plantas inoculadas com os isolados UFSC-Pt116, UFSC-Pt188 e UFSC-SA9 alcançaram maior altura, diâmetro do caule, massa seca da parte aérea e volume de raízes em relação ao controle. Plantas inoculadas com o isolado de fungo ectomicorrízico UFSC-Pt188 apresentaram maior teor de fósforo e potássio na parte aérea que as plantas não inoculadas. A inoculação com o isolado fúngico ectomicorrízico UFSC-Pt116 promoveu maior altura e massa seca da parte aérea. Para os teores de nitrogênio e potássio, e para massa seca de raízes não foram observadas diferenças significativas entre os tratamentos. A inoculação com os fungos ectomicorrízicos UFSC-Pt116, UFSC-SA9 e UFSC-Pt188 isoladamente, promoveram maior altura, diâmetro de caule, acúmulo de massa seca da parte aérea e volume de raízes das plantas de Eucalyptus grandis.

ABSTRACT In Rio Grande do Sul state, the eucalyptus planted forests are cultivated in low fertility soils, which contribute to ectomycorrhizal association. This study evaluated the effect of ectomycorrhizal isolates UFSC-Pt116, UFSC-Pt188 and UFSC-SA9 inoculation, individually and in combination, with Eucalyptus grandis in Quartzarenic Neosols. Evaluations were performed at 30, 45, 60, 75 and 90 days after sowing. Plants inoculated with isolates UFSC-Pt116, UFSC-Pt188 and UFSC-SA9 showed highest height, stem diameter, dry mass of shoot and root volume than the control. Plants inoculated with the ectomycorrhizal fungus isolate UFSC-Pt188 showed highest content of phosphorus and potassium in shoots than non-inoculated plants. Inoculation individual ectomycorrhizal isolate UFSC-Pt116 promoted the highest height and shoot dry mass. For nitrogen and potassium, and root biomass have not showed significant differences between treatments. Then inoculation with ectomycorrhizal UFSC-Pt116, UFSC-Pt188 and UFSC-SA9 alone promoted highest height, stem diameter, dry mass of shoot and plant root volume of Eucalyptus grandis.

Eucalypts is one of the main species used for commercial reforestation in the state of Rio Grande do Sul, Brazil. This study aimed to evaluate the survival and early growth of eucalyptus trees in an area subject to sandy process after three years of growth. The Eucalyptus grandis seedlings were grown in a greenhouse, innoculated or not with the isolated ectomycorrhizal Pisolithus microcarpus (UFSC-Pt116), produced in peat or Entisol. After 120 days, the seedlings were transplanted to an area subject to the sandy process, in the city of São Francisco de Assis, RS. The plants have been evaluated regarding survival, height, stem diameter, nitrogen, phosphorus and potassium levels and total phosphorus, inorganic phosphorus, organic phosphorus and wood production on different days after planting. The seedlings grown on the Entisol which was inoculated with the isolated UFSC-Pt116 presented higher survival rates, height, stem diameter, nitrogen concentration and wood production compared to the non-inoculated seedlings. Inoculation with ectomycorrhizal fungi enhanced the production of E. grandis seedlings in survival rates, height, stem diameter.

RESUMO No Estado do Rio Grande do Sul, os reflorestamentos de eucalipto têm se concentrado em solos com baixa fertilidade natural, e o desempenho dessas mudas poderá depender da formação da associação ectomicorrízica. Nesse trabalho, avaliou-se o efeito da inoculação dos isolados de fungos ectomicorrízicos UFSC-Pt116, UFSC-Pt188 e UFSC-SA9, individualmente e em mistura, sobre mudas de Eucalyptus grandis. As avaliações foram realizadas aos 30, 45, 60, 75 e 90 dias após semeadura. A inoculação individual do isolado fúngico ectomicorrízico UFSC-Pt116 promoveu maior altura e massa seca da parte aérea. As mudas inoculadas com mistura dos isolados fúngícos UFSC-Pt116 + UFSC-Pt188 + UFSC-SA9 acumularam maior quantidade de fósforo aos 90 dias. Para os teores de nitrogênio e potássio, e massa seca de raízes não mostrou diferença significativa entre os tratamentos.

ABSTRACT In the Rio Grande do Sul state, where eucalyptus reforestation is common in low fertility soils, the seedling performance may depend on the ectomycorrhizal association. In this paper, the inoculation effects of UFSC-Pt116, UFSC-Pt188 and UFSC-SA9 ectomycorrhizal fungi isolates, individually and in mixture, on Eucalyptus grandis seedlings were evaluated. Evaluations were performed at 30, 45, 60, 75, and 90 days after sowing. The individual inoculation of UFSC-Pt116 isolate promoted highest height and aerial dry mass. The seedlings inoculated with the mixture UFSC-Pt116 + UFSC-Pt188 + UFSC-SA9 accumulated highest amounts of phosphorus at 90 days. The nitrogen and potassium concentrations, and root dry mass did not show significant differences among the treatments.