Abstract: Yerba mate (Ilex paraguariensis St. Hill.) is an important woody tree in South America, however the production of quality seedlings is a major problem. Microorganisms that promote plant growth have shown to be efficient biotechnologies in the production of seedlings. The arbuscular mycorrhizal fungi (AMF), it establishes symbiosis with several plant species and increases the accumulation of biomass and absorption of poorly mobile nutrients such as phosphorus. Here, we test the effects of two AMF species on growth, root architecture, phosphorus accumulation and gas exchange of yerba mate seedlings cultivated under different phosphorus levels. We used seedlings in a non-sterile soil, inoculated with AMFs Rhizophagus clarus SCT720A and Acaulospora colombiana SCT115A, and non-inoculated (control) treatment under five levels of phosphorus (0; 25; 50; 100 and 200% recommendation). After 90 days of AMF inoculation, plant dry biomass, root architecture and mycorrhizal colonization were determined and after 180 days, the same parameters plus photosynthetic rate, transpiration rate, stomatal conductance and P content were evaluated. AMF inoculation increased shoot and root dry biomass, total root length, root volume. Plants inoculated with AMF showed higher photosynthesis rate. Phosphorus content and mycorrhizal colonization were increased almost three times when inoculated with AMF. Our findings highlight the importance of AMF inoculation for Ilex paraguariensis seedlings production, reducing the time needed in nurseries to enhance tree performance.

Abstract Brazil is considered a megadiverse country, but the soil fauna is still very poorly known. The aim of this study was to report, for the first time, the abundance and genus composition of terrestrial enchytraeids (Enchytraeidae, Oligochaeta) in Savanna Tall Woodland (Cerradão) and a pasture in Cerrado Biome and in Upper Montane Atlantic Forest and a grassland in Atlantic Forest Biome. The enchytraeid density in Pasture and Cerradao was 2,036 and 18,844 (204 and 2,094, on average) individuals per square meter, respectively. At the Atlantic forest and Grassland, density was 9,666 and 12,242 individuals per square meter (1,075 and 1,471 on average). About genus composition for the studied areas, Enchytraeus and Hemienchytraeus were found in the four ecosystems evaluated, while Tupidrilus and Fridericia were found only in Cerradão and Atlantic Forest, respectively. Achaeta was absent in Upper Montane Atlantic Forest, but dominant in pasture, while Guaranidrilus was absent in Pasture, but predominant in the other ecosystems.

ABSTRACT: This study aimed to evaluate the relationship of edaphic fauna under a no-tillage system with different levels of soybean productivity [High (NTH), Medium (NTM) and Low (NTL)] in the west of Santa Catarina (Brazil), identifying which chemical and physical variables most affect them, and the best indicators that can be used. Native forest (NF) areas were used as a reference. A total of 207 samples of soil fauna were collected by soil monolith and pitfall trap methods over two years of evaluation in four municipalities. Based on edaphic fauna data, Shannon-Wiener (H’), Pielou (J), Dominance (D), Margalef and Fisher Alpha (α) indices were generated, in addition to the average richness and abundance. Data from NTs were submitted to analysis of variance and compared by Tukey's test (p > 0.05). The NF was used as a reference and compared with the agriculture system by Dunnett test (p > 0.05), and regressions between soybean productivity and diversity indices. The H’, Margalef, α indices, and average richness for soil fauna sampled by soil monoliths followed the productivity gradient NTH > NTM > NTL, showing a positive correlation with the increase of soybean productivity. NTH has a diversity index similar to that of NF. Soybean productivity is affected by the richness and diversity of edaphic fauna, but abundance was not sensitive in predicting treatments under no-tillage; Fisher's alpha index was more sensitive in treatment separation with soil monoliths. The environmental variables aluminum, organic matter, phosphorus, potassium and penetration resistance affect the fauna edaphic.

Abstract This study aimed to evaluate the abundance and diversity of Coleoptera in five land use systems (LUS) and the soil properties that explain the distribution of these organisms. Uses involved native forest (NF), Eucalyptus plantation (EP), perennial pasture (PA), integrated crop-livestock (ICL) and no-tillage (NT) in western Santa Catarina, Brazil. Coleopterans were sampled by the methods of pitfall traps and soil monoliths during the winter and summer. Regardless of the LUS, 1,441 individuals were captured, with Staphylinidae being the most representative family (~47%). The use of NF showed higher abundances of coleopterans. The land use systems PA, NT, and ICL obtained high values of diversity of Coleoptera families, depending on the method and season of collection. The distribution of families was influenced by the sampling season, and some soil properties such as biopores, water content and phosphorus can explain the variation of abundance among the LUS.

Resumo: O objetivo deste estudo foi avaliar a influência do uso do solo na diversidade morfológica de colêmbolos e verificar a relação destes organismos com os atributos físicos, químicos e microbiológicos do solo. Foram coletadas amostras na região Sul de Santa Catarina, envolvendo três municípios: Orleans, Lauro Müller e Siderópolis, nos sistemas de uso do solo (SUS) de floresta nativa (FN), reflorestamento de eucalipto (RE), pastagem perene (PA), integração lavoura-pecuária (ILP) e plantio direto (PD). As coletas de solo para determinação dos atributos edáficos e a instalação de armadilhas de queda, foram realizadas no inverno e verão, nos mesmos pontos. Os colêmbolos coletados foram contados e morfotipados e os dados foram analisados por meio da abundância, diversidade de Shannon-Wiener (H') e Margalef, índice de dominância de Simpson (D), uniformidade de Pielou (J), riqueza de morfotipos e Análise de Componentes Principais (ACP). Os morfotipos de Collembola foram influenciados pelas condições de manejo de cada sistema, sobretudo o impacto dos SUS nesses organismos depende da intensidade das práticas florestais/agrícolas utilizadas, incluindo rotações culturais e preparo do solo.

Abstract: The aim of this study was to evaluate the influence of soil use on the morphological diversity of springtails and to verify the relationship of these organisms with soil physical, chemical, and microbiological properties. Samples were collected in the Southern region of Santa Catarina, involving three municipalities: Orleans, Lauro Müller, and Siderópolis, in the land use systems (LUS) of native forest (NF), Eucalyptus plantation (EP), pasture (PA), integrated crop-livestock (ICL), and no-tillage (NT). Soil samples to determine edaphic properties and pitfall traps were collected in winter and summer, in the same areas. The collected springtails were counted and morphotyped and the data were analyzed through abundance, Shannon-Wiener diversity (H') and Margalef index, Simpson dominance index (D), Pielou evenness index (J), morphotype richness, and Principal Components Analysis (PCA). Springtails morphotypes were influenced by the management conditions of each system, especially the impact of LUS on these organisms depends on the intensity of the forest/agricultural practices used, including crop rotation and soil preparation.

ABSTRACT: Springtails (Collembola) are soil organisms with wide morphological diversity and are sensitive to alterations in the soil, regardless of whether they are human-caused or not. The aim of this study was to evaluate the influence of land use on the morphological diversity of springtails and verify their relationships with soil physical, chemical, and microbiological properties. Samples were collected in the eastern region of Santa Catarina, in three municipalities: Joinville, Blumenau, and Timbó. They included the following land use systems (LUSs): native forest (NF), Eucalyptus plantation (EP), pasture (PA), integrated crop-livestock (ICL), and no tillage (NT). Samples were collected to determine soil properties, and pitfall traps were set in the winter and summer at the same points. The captured springtails were counted and morphotyped, observing features such as presence or absence of ocelli and setae, pigmentation, antenna length, and furcula length. The data were analyzed based on abundance, the Shannon-Wiener (H') and Margalef diversity indices, Pielou's evenness index (J), morphotype richness, modified Soil Biological Quality index (QBS), and Principal Component Analysis (PCA). Springtails abundance was higher in ICL and PA, whereas morphotype richness was higher in NF and ICL in the winter. The Shannon-Wiener and Margalef indices were higher in the winter in NF. In the summer, only H' differed significantly among the LUSs and was higher in NF. The QBS values did not precisely follow the human intervention gradient in either of the two periods. The PCA showed difference among the periods and LUSs. In the winter, the occurrence of morphotypes was related to soil microbiological and chemical properties, whereas in the summer, the distribution of morphotypes was explained by soil physical and chemical properties. Morphological diversity analysis is a good alternative to study springtail distribution and soil biological quality, especially when associated with multivariate techniques.

ABSTRACT Coleopterans (Coleoptera) are major ecosystem service providers. However ecomorphological features that are comparable in a wide range of invertebrates within this group and in various environments must be found, to be able to study regions with different species, contributing to overcome difficulties of the taxonomic approach and understand the functioning of ecosystems. This research addressed the diversity of Coleoptera, using a methodology of ecomorphological traits, as well as their relation with the land use systems (LUS) and the soil properties. The following LUS were evaluated: no-tillage (NT), crop-livestock integration (CLI), pasture (PA), Eucalyptus stands (EST), and native forest (NF). Samples were collected using a 3 × 3 point grid (sampling points at a distance of 30 m), in winter and summer, in three municipalities on the Southern Santa Catarina Plateau, Brazil. Coleopterans were collected using the methodology recommended by the Tropical Soil Biology and Fertility Program, based on the excavation of soil monoliths, and on pitfall traps. To evaluate the biological forms (morphotypes) and ecomorphological groups, the ecomorphological index (EMI) methodology was adopted and the modified soil biological quality (SBQ) index was determined. At the same points, samples were collected to evaluate environmental variables (soil physical, chemical, and microbiological properties). Density data underwent nonparametric univariate statistical analysis and multivariate abundance to verify the distribution of coleopterans in the LUS, and the environmental variables were considered as explanatory. Regardless of the LUS, 14 morphotypes were identified, and adult coleopterans with epigean morphologic adaptations were more abundant than hemi-edaphic and edaphic coleopterans, respectively. Morphotype diversity was higher in the systems NF, EST, and PA in summer and in NT in winter. The reductions in SBQ index were not associated with a gradient of land use intensification (NF> EST> PA> CLI> NT), and the index was higher for NF and lower for EST. Principal component analysis (PCA) indicated a different distribution of invertebrates between the LUS. For the edaphic species, better adapted to life in the soil, a relation with NT and CLI was observed, due to more favorable pH values and phosphorus content. In the NF, a greater amount of morphotypes was identified, and the properties related to soil carbon dynamics contributed to explain this distribution. Separation at the morphotype level, taking adaptation level to soil life into consideration, has proved efficient to discriminate the LUS, mainly along with other explanatory environmental variables.

ABSTRACT: Collembolan species are differently affected by soil tillage (conventional, minimum tillage, and no-tillage) and are known to modify plant growth. This study relies on the relationships between Collembola community structures and land use systems as a proxy for characterizing changes in soil quality. Thus, Collembola community structure (eco-morphological groups - edaphic, hemiedaphic and epigeic, and morphotypes) were examined in a no-tillage system and crop-livestock integration system to evaluate the discriminative power of the Collembola community structure and to determine which soil properties drives structural diversity. Thirty-eight morphotypes of Collembola were recorded in this study, 11 belonging to the edaphic eco-morphological group, 14 hemiedaphic, and 13 epigeic. The hemiedaphic and epigeic groups, in the no-tillage system, were more influenced by changes in soil properties (total organic carbon, particulate organic carbon, total N, Ca, Mg, moisture, bulk density) and mycelium length than the groups in the crop-livestock integration system (mycorrhizal inoculum potential, and soil properties as dehydrogenase, particulate organic carbon, Mg, sand). Collembola eco-morphological groups were better predictors for ecosystem functioning than Collembola density and can be used to distinguish differences between soil uses, reducing laboratory analysis time.

ABSTRACT Intensive land use can affect macrofaunal biodiversity, which is a property that can be used as a soil quality indicator. This study evaluated the abundance and diversity of soil macrofauna and its relation to soil chemical and physical properties in five land use systems (LUS) in the eastern region of Santa Catarina. The following LUS were studied: native forest (NF), eucalyptus plantations (EP), perennial pasture (PP), integrated crop-livestock (ICL), and no-tillage cropping (NT). The macrofauna was quantified in 0.25 × 0.25 m monoliths and sampled in the 0.00-0.20 m layer in the summer (Jan/2012) and winter (Jul/2012). For each LUS, nine points were sampled, distributed in a 30 × 30 m sampling grid. After screening the edaphic macrofauna organisms, the individuals were counted and identified at the species level when possible, or in major taxonomic groups. The Shannon diversity indices were calculated and the macrofaunal groups together with the physical and chemical properties were subjected to principal component (PCA) and redundancy analysis (RDA). The abundance and diversity of macrofaunal groups are affected by the LUS. The properties of organic matter, macroporosity, bulk density, cation exchange capacity at pH 7.0, base saturation, potential acidity, and exchangeable Al were related to the abundance of soil macrofaunal groups. The stability and biodiversity of soil macrofauna were highest in the LUS of NF, PP, and EP.

O presente estudo teve como objetivo avaliar as características físicas, químicas e biológicas do solo, a composição mineral e a qualidade de frutos, em pomares de maçãs 'Royal Gala' conduzidos sob os sistemas de produção convencional (CON) e orgânico (ORG), em um Nitossolo Háplico. Na linha de cultivo das plantas, o solo no ORG apresentou melhor qualidade física (maiores valores de estabilidade dos agregados, condutividade hidráulica saturada e porosidade total, e menor densidade), química [menor acidez e maiores valores de Ca e Mg trocáveis, carbono orgânico total (COT) e nitrogênio total (NT)] e biológica [maiores valores de carbono da biomassa microbiana (Cmic) e relação Cmic/COT], na camada de 0-20 cm, quando comparado ao CON. Como no ORG não foram utilizados produtos químicos sintéticos para a superação de dormência, a colheita comercial dos frutos ocorreu um mês após o CON. Apesar desta diferença na época de colheita, frutos cultivados sob o sistema ORG apresentam na colheita menor índice de iodo-amido e maiores valores de firmeza de polpa e teor de sólidos solúveis, quando comparados aos valores obtidos em frutos cultivados sob o sistema CON. Frutos do ORG possuem maior percentagem de coloração vermelha da casca, porém elevada severidade de "russeting", em relação aos do sistema CON. Durante o armazenamento refrigerado convencional (quatro meses a 0 ± 0,5 ºC/90-95% UR), frutos cultivados sob o sistema ORG apresentam elevada perda de firmeza de polpa, o que pode estar associado aos altos teores K e Mg na polpa e de N na casca, em relação aos cultivados sob o sistema CON. Portanto, mesmo no sistema ORG, o suprimento destes elementos pode ser demasiadamente elevado, comprometendo a preservação da qualidade pós-colheita dos frutos.

The present study aimed to evaluate the physical, chemical and biological characteristics of the soil, and the mineral composition and quality of the fruit, in orchards of 'Royal Gala' apple, under conventional (CON) and organic (ORG) production systems, in a Haplic Nitisol. Under ORG, the soil in the cultivation furrow showed better physical quality (higher values for aggregate stability, saturated hydraulic conductivity and porosity, and lower density), chemical quality [lower acidity and higher values of exchangeable Ca and Mg, total organic carbon (TOC) and total nitrogen (TN)] and biological quality [higher values for microbial biomass carbon (Cmic) and ratio of Cmic to TOC], in the 0-20 cm layer compared to CON. Because under the ORG system synthetic chemicals for breaking dormancy were not used, commercial fruit harvesting took place one month after that of the CON system. Despite this difference in the time of harvest, fruit grown under the ORG system have, when harvested, a lower starch-iodine index and higher values for firmness and soluble solid content, when compared to values obtained in fruits grown under the CON system. Fruit under ORG has a higher percentage of red skin coloration, but more severe russeting, in relation to that under CON. During conventional cold storage (four months at 0 ± 0.5 ºC / 90-95% RH), fruit grown under the ORG system show a high loss in pulp firmness, which may be associated with the high levels of K and Mg in the pulp and of N in the skin, compared to fruit grown under the CON system. Therefore, even under the ORG system, the supply of these elements may be too high, compromising the preservation of the postharvest quality of the fruit.

Visando estudar a influência de diferentes sistemas de manejo do solo com e sem calagem, sobre a colonização micorrízica radicular e a produção de micélio extrarradicular, por meio de técnica de análise multivariada, utilizou-se um experimento implantado em 1978, no município de Guarapuava, PR. A análise de componentes principais comprovou a existência de efeitos negativos do sistema de preparo convencional do solo sobre a colonização de fungos micorrízicos arbusculares (FMAs) do solo, principalmente em estruturas como arbúsculos e vesículas. A calagem apresentou benefícios para os parâmetros de colonização micorrízica e comprimento de micélio extrarradicular, sendo mais significativo nos sistemas de manejo conservacionistas, principalmente o sistema de plantio direto. Nas áreas de sistemas convencionais ocorreu uma redução na colonização micorrízica e, conseqüentemente, diminuição dos efeitos benéficos dos FMAs para as plantas, reduzindo a qualidade do solo e a sustentabilidade.

The objective of this work was to evaluate the influence of different soil management systems with and without liming on root colonization and production of extraradicular mycelium. Through multivariate analysis technique, an experiment established in 1978 in Guarapuava, state of Paraná was used. Correspondence analysis proved the existence of negative effects of the conventional tillage on the root mycorrhizal colonization (AMF) of the soil, mainly in structures as arbuscules and vesicles. The liming showed to be beneficial for the parameters of root micorrhyzal colonization and hyphal length, being more significant for conservationist management systems, such as no-tillage. In the areas under conventional management systems there was a reduction in micorrhyzal root colonization and consequently a decrease in beneficial effects of AMF for the plants, reducing the quality of the soil and the sustainability.

O uso da cobertura do solo é alternativa para o controle de plantas daninhas. Entretanto há poucos estudos sobre seu efeito na qualidade do solo. Avaliou-se, em duas estações do ano, o efeito de tipos de cobertura do solo nos atributos microbianos de um Latossolo com produção integrada de maçãs no sul do Brasil. O experimento foi conduzido em blocos ao acaso em Vacaria, RS. As coberturas estudadas foram: acícula, serragem e plástico preto comparativamente ao tratamento controle (infestado). As amostras de solo foram coletadas em fevereiro e agosto de 2006, sendo avaliados atributos relacionados ao carbono, ao nitrogênio e ao fósforo. As coberturas orgânicas (acícula e pínus) promoveram no solo menor temperatura e maior umidade, além de maiores teores de carbono e nitrogênio microbiano, relação Cmic:Corg, Nmic:Norg e Cmic:Nmic quando comparadas ao solo sob plástico preto; já o fósforo microbiano foi maior no inverno. A cobertura com serragem promoveu as melhores condições para os compartimentos microbianos no inverno, sendo que nessa mesma estação, as coberturas incrementaram o compartimento microbiano comparativamente ao tratamento controle, infestado com plantas daninhas.

The use of mulching is an alternative to control weeds but there are few studies on its effect on soil quality. In this sense, this study aimed to evaluate the effect of types of mulching on the attributes of microbial carbon, nitrogen and phosphorus in a Typic Hapludox with production of integrated apples in southern Brazil. The experiment was conducted in randomized blocks in the Vacaria, state of Rio Grande do Sul, southern Brazil. The soil mulch types studied were: pine needle, sawdust, black plastic and a control. The soil samples were collected in February (summer) and August (winter) of 2006, and the attributes related to total organic and microbial carbon, nitrogen and phosphorus were determined. Organic mulchings (pine needle and sawdust) promoted lower soil temperature, and greater moisture, microbial carbon (Cmic), microbial nitrogen (Nmic), and the ratios Cmic:Corg, Nmic:Norg and microbial C:N than black plastic. Microbial phosphorus was greater in winter. Sawdust mulching promoted the best conditions to microbial biomass in winter. The mulch types increased the microbial compartment in winter as compared to the nonweeded control .

O uso de coberturas sobre o solo constitui-se em alternativa na prevenção de plantas invasoras nos plantios orgânicos que excluem a utilização de herbicidas. Entretanto, existem poucos estudos no sul do Brasil sobre a implicação da cobertura do solo em sua qualidade microbiológica. Assim, o objetivo deste trabalho foi avaliar em duas épocas distintas o efeito de diferentes tipos de cobertura do solo nos atributos de carbono, nitrogênio e fósforo microbiano de um Latossolo com produção orgânica de maçã no sul do Brasil. O estudo foi realizado na Estação Experimental da Embrapa em Vacaria (RS) em delineamento experimental de blocos ao acaso. As coberturas estudadas foram: acícula, serragem e plástico preto comparadas ao solo descoberto e com plantas invasoras. As amostras de solo foram coletadas em fevereiro (verão) e agosto (inverno) de 2006, sendo determinados atributos microbianos e químicos relacionados ao carbono, nitrogênio e fósforo. As coberturas orgânicas (acícula e serragem) promoveram maior umidade e maiores teores de Cmic, Nmic, Corg, maior relação Cmic/Corg, Nmic/Ntotal e C/N microbiano. A cobertura com plástico preto e solo descoberto promoveu maior temperatura, nitrato, quociente metabólico e fósforo imobilizado na biomassa. Com base neste estudo e considerando a qualidade microbiana do solo as melhores coberturas foram as orgânicas.

The use of soil mulching is an alternative in the prevention of weeds in organic orchard, which exclude the use of herbicides. However, there are few studies in southern Brazil on the impact of soil mulching in the soil microbiological quality. In this sense, the purpose of this study was to evaluate in two different seasons the effect of different types of soil mulching in the attributes of microbial carbon, nitrogen and phosphorus in a Typic Hapludox producing of organic apples in southern Brazil. The study was conducted at the Experimental Station of Embrapa in Vacaria, Rio Grande do Sul State, in a randomized block design. The mulchings were: pinus needle, wooden dust and black plastic compared to bare soil and weeds. Soil samples were collected in February (summer) and August (winter), 2006, with analysis microbial and chemical attributes related to carbon, nitrogen and phosphorus. Organic mulching (pinus needle and wooden dust) promoted higher soil moisture and higher levels of Cmic, Nmic, Corg, greater ratio Cmic/Corg, Nmic/Ntotal and microbial C/N. Black plastic mulching and bare soil promoted higher temperature, nitrate, immobilized phosphorus in biomass and metabolic quotient. Based on this study and considering soil microbial quality the best mulching were the organics.

O objetivo do trabalho foi avaliar o uso do inoculante associado ao uso de adubação foliar de Co+Mo sobre a produtividade de grãos, acúmulo de nutrientes nos grãos de feijão comum, cv FT Nobre. Testaram-se 3 doses de inoculante (0, 200 e 400 g/ 50 kg de sementes) combinadas com 4 níveis de adubação foliar de Co+Mo, (T0=0 e 0; T1=4,9 e 49; T2=7,3 e 73; e T3=9,7 e 97 g ha-1 de Co e Mo, respectivamente). A produtividade dos grãos com o uso de inoculante (400 g / 50 kg de sementes) associado a alto nível de Co+Mo (T2 e T3) foi semelhante ao fornecimento de nitrogênio mineral (70 kg ha-1). O aumento das doses de inoculante também favoreceu o aumento dos teores de proteína, P e Mg nos grãos. Esses resultados indicam que o nitrogênio na forma de fertilizante mineral pode ser substituído pela prática da inoculação das sementes de feijão associado à adubação foliar de Co+Mo.

The objective of this work was to evaluate the efficiency of nitrogen fixing inoculum associated with Co + Mo leaf spray on the common bean grain yield and grain nutrients, cv. FT Nobre. Three dosages of the inoculant (0, 200 and 400 g/50 kg seeds), combined with four Co + Mo leaf spray levels (T0=0,0; T1=4.9,49; T2=7.3,73; and T3=9.7,97 g ha-1 of Co and Mo, respectively) were tested. The grain yield with the use of the inoculant (400 g / 5O kg seed-1) associated with the higher level of Co+Mo (T2 and T3) was very similar to the mineral nitrogen condition fertilizer recommended for the bean (70 kg ha-1 of N). With the increased inoculant dosage, an increase of the protein content and of P and Mg in the grain was also observed. The results indicated that the mineral nitrogen source could be replaced by inoculation of the seeds with Rhizobium tropici combined with Co + Mo leaf spray.

Objetivou-se avaliar a densidade de populações de bactérias diazotróficas associativas em amostras de solos e de raízes de gramíneas oriundas de sítios contaminados com metais pesados, e caracterizar isolados destas populações através da análise fenotípica (tolerância aos metais pesados zinco e cádmio e à NaCl in vitro, perfis protéicos), e genotípica (seqüenciamento de 16S rDNA), comparados às estirpes tipo das mesmas espécies. As densidades foram avaliadas nos meios NFb, Fam e LGI, comumente utilizados para culturas de enriquecimento de populações de bactérias diazotróficas associativas. As densidades encontradas em amostras de solo e raiz de sítios contaminados foram semelhantes àquelas relatadas na literatura para solos agrícolas. Isolados de Azospirillum spp. de solos contaminados e estirpes tipo oriundas de solos não contaminados variaram substancialmente com relação à tolerância a Zn+2 e Cd+2, sendo que Cd+2 mais tóxico que Zn+2. Dentre os isolados mais tolerantes (UFLA 1S, 1R, S181, S34, e S22), alguns(1R, S34 e S22) foram mais tolerantes a metais pesados que rizóbios isolados de solos de áreas tropicais e temperadas. A maioria dos isolados mais tolerantes a metais pesados também foi tolerante ao estresse salino, o que foi indicado por seu crescimento em meio sólido suplementado com 30 g L-1 de NaCl in vitro. Cinco isolados apresentaram alta dissimilaridade em perfis protéicos e o seqüenciamento do gene 16S rDNA em dois deles revelou que apresentam novas seqüências de Azospirillum.

This work aimed to evaluate density of associative diazotrophic bacteria populations in soil and grass root samples from heavy metal contaminated sites, and to characterize isolates from these populations, both, phenotypically (Zinc, Cadmium and NaCl tolerance in vitro, and protein profiles) and genotypically (16S rDNA sequencing), as compared to type strains of known diazotrophic species. Densities were evaluated by using NFb, Fam and JNFb media, commonly used for enrichment cultures of diazotrophic bacteria. Bacterial densities found in soil and grass root samples from contaminated sites were similar to those reported for agricultural soils. Azospirillum spp. isolates from contaminated sites and type strains from non-contaminated sites varied substantially in their in vitro tolerance to Zn+2 and Cd+2, being Cd+2 more toxic than Zn+2. Among the most tolerant isolates (UFLA 1S, 1R, S181, S34 and S22), some (1R, S34 and S22) were more tolerant to heavy metals than rhizobia from tropical and temperate soils. The majority of the isolates tolerant to heavy metals were also tolerant to salt stress as indicated by their ability to grow in solid medium supplemented with 30 g L-1 NaCl. Five isolates exhibited high dissimilarity in protein profiles, and the 16S rDNA sequence analysis of two of them revealed new sequences for Azospirillum.