The impact of land-use changes and management intensification on bacterial communities in the last decade: a review.

In the last decade, advances in soil bacterial ecology have contributed to increasing agricultural production. Brazil is the world leading agriculture producer and leading soil biodiversity reservoir. Meanwhile, there is still a significant gap in the knowledge regarding the soil microscopic life and its interactions with agricultural practices, and the replacement of natural vegetation by agroecosystems is yet to be unfolded. Through high throughput DNA sequencing, scientists are now exploring the complexity of soil bacterial communities and their relationship with soil and environmental characteristics. This study aimed to investigate the progress of bacterial ecology studies in Brazil over the last 10 years, seeking to understand the effect of the conversion of natural vegetation in agricultural systems on the diversity and structure of the soil microbial communities. We conducted a systematic search for scientific publication databases. Our systematic search has matched 62 scientific articles from three different databases. Most of the studies were placed in southeastern and northern Brazil, with no records of studies about microbial ecology in 17 out of 27 Brazilian states. Out of the 26 studies that examined the effects of replacing natural vegetation with agroecosystems, most authors concluded that changes in soil pH and vegetation cover replacement were the primary drivers of shifts in microbial communities. Understanding the ecology of the bacteria inhabiting Brazilian soils in agroecosystems is paramount for developing more efficient soil management strategies and cleaner agricultural technologies.

Biogeographic responses and niche occupancy of microbial communities following long-term land-use change.

Understanding the effects of forest-to-agriculture conversion on microbial diversity has been a major goal in soil ecological studies. However, linking community assembly to the ruling ecological processes at local and regional scales remains challenging. Here, we evaluated bacterial community assembly patterns and the ecological processes governing niche specialization in a gradient of geography, seasonality, and land-use change, totaling 324 soil samples, 43 habitat characteristics (abiotic factors), and 16 metabolic and co-occurrence patterns (biotic factors), in the Brazilian Atlantic Rainforest, a subtropical biome recognized as one the world's largest and most threatened hotspots of biodiversity. Pairwise beta diversities were lower in pastures than in forest and no-till soils. Pasture communities showed a predominantly neutral model, regarding stochastic processes, with moderate dispersion, leading to biotic homogenization. Most no-till and forest microbial communities followed a niche-based model, with low rates of dispersal and weak homogenizing selection, indicating niche specialization or variable selection. Historical and evolutionary contingencies, as represented by soil type, season, and dispersal limitation were the main drivers of microbial assembly and processes at the local scale, markedly correlated with the occurrence of endemic microbes. Our results indicate that the patterns of assembly and their governing processes are dependent on the niche occupancy of the taxa evaluated (generalists or specialists). They are also more correlated with historical and evolutionary contingencies and the interactions among taxa (i.e., co-occurrence patterns) than the land-use change itself.

First record on enchytraeids in a Savanna Tall Woodland (Cerradão) and Upper Montane Atlantic Forest in Brazil.

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.

Biogeographic Patterns of Arbuscular Mycorrhizal Fungal Communities Along a Land-Use Intensification Gradient in the Subtropical Atlantic Forest Biome.

Information concerning arbuscular mycorrhizal (AM) fungal geographical distribution in tropical and subtropical soils from the Atlantic Forest (a global hotspot of biodiversity) are scarce and often restricted to the evaluation of richness and abundance of AM fungal species at specific ecosystems or local landscapes. In this study, we hypothesized that AM fungal diversity and community composition in subtropical soils would display fundamental differences in their geographical patterns, shaped by spatial distance and land-use change, at local and regional scales. AM fungal community composition was examined by spore-based taxonomic analysis, using soil trap cultures. Acaulospora koskei and Glomus were found as generalists, regardless of mesoregions and land uses. Other Acaulospora species were also found generalists within mesoregions. Land-use change and intensification did not influence AM fungal composition, partially rejecting our first hypothesis. We then calculated the distance-decay of similarities among pairs of AM fungal communities and the distance-decay relationship within and over mesoregions. We also performed the Mantel test and redundancy analysis to discriminate the main environmental drivers of AM fungal diversity and composition turnover. Overall, we found significant distance-decays for all land uses. We also observed a distance-decay relationship within the mesoregion scale (< 104 km) and these changes were correlated mainly to soil type (not land use), with the secondary influence of both total organic carbon and clay contents. AM fungal species distribution presented significant distance-decays, regardless of land uses, which was indicative of dispersal limitation, a stochastic neutral process. Although, we found evidence that, coupled with dispersal limitation, niche differentiation also played a role in structuring AM fungal communities, driven by long-term historical contingencies, as represented by soil type, resulting from different soil origin and mineralogy across mesoregions.

Ecotoxicological test to assess effects of herbicides on spore germination of Rhizophagus clarus and Gigaspora albida.

Given the essential role of arbuscular mycorrhizal fungi (AMF) in soil systems and agriculture, their use as biological indicators has risen in all fields of microbiology research. However, AMF sensitivity to chemical pesticides is poorly understood in field conditions, and not explored in ecotoxicology protocols. Hence, the goal of this study was to evaluate the effects of different concentrations of glyphosate (Roundup®) and diuron+paraquat (Gramocil®) on the germination of spores of Gigaspora albida and Rhizophagus clarus in a tropical artificial soil. This study was conducted in 2019 at the Soil Ecology and Ecotoxicology Laboratory of the Universidade do Estado de Santa Catarina. The nominal concentrations of glyphosate were 0, 10, 50, 100, 250, 500, 750 and 1000 mg a.i. kg-1. For diuron+paraquat, the concentrations tested were 0, 10 + 20, 50 + 100, 100 + 200, 250 + 500, 500 + 1000, 750 + 1500 and 1000 + 2000 mg a.i. kg-1. Glyphosate did not alter germination of G. albida, but germination inhibition of R. clarus spores was of 30.8% at 1000 mg kg-1. Diuron+paraquat inhibited by 8.0% germination of G. albida, but only at the highest concentration tested. On the other hand, effects on R. clarus were detected at 50 + 100 mg kg-1 concentration and above, and inhibition was as high as 57.7% at the highest concentration evaluated. These results suggest distinct response mechanisms of Rhizophagus and Gigaspora when exposed to herbicides, with the former being more sensitive than the later.

Are there any risks of the disposal of pesticide effluents in soils? Biobed system meets ecotoxicology ensuring safety to soil fauna.

The biobed is a purification system, which reduces soil pollution for receiving pesticide residues from handling and washing machinery in agricultural areas. The aims of this study were (1) to assess ecotoxicity effects over time to soil fauna, posed by Lorsban® 480 BR (Chlorpyrifos) and Dithane® NT (Mancozeb) residues when disposed of in a biobed system compared with two subtropical soils, and (2) to assess ecotoxicity effects over time to soil fauna simulating an accidental spillage with Lorsban® 480 BR at the biobed. A semi-field experiment was conducted for 420 days in southern Brazil, testing continuous disposal of washing pulverization tanks in biobeds, Typic Haploperox or Typic Hapludults. In addition, different biobeds received a single dose (1 L) of Lorsban® 480 BR to simulate an accidental spillage. Chronic ecotoxicity tests were performed using Folsomia candida, Eisenia andrei, and Enchytraeus crypticus in different sampling times for both experiments. F. candida was the most sensitive species. The biobed system was able to eliminate effects from residues of both pesticides over time in all species, which did not happen in both natural soils. In accidental spillage simulation, even 420 days after contamination, F. candida did not show reproduction. The biobeds can be a feasible alternative for the disposal and treatment residues of pesticides, also for handling and washing pesticides activities. The system was efficient in promoting degradation and reducing ecotoxicity effects posed by Lorsban® 480 BR and Dithane® NT for soil fauna. It is a safe alternative to avoid soil contamination.

Disentangling the effects of the aqueous matrix on the potential toxicity of liquid pig manure in sub-tropical soils under semi-field conditions.

Inadequate application of liquid pig manure (LPM) may pose risks to the soil due to the potential contaminants that exists, as well as by the large water input that can originate excessive moisture. By using Terrestrial Model Ecosystems, this study aimed to evaluate the effect of application of LPM (82% moisture) using the application rates of 20, 50 and 150 m3 ha-1 and also of the corresponding amount of water to understand the origin of effects on the soil fauna of two sub-tropical soils. In general, the results obtained for the two soil types indicated that LPM (150 m3 ha-1) changed the composition of soil fauna, with an increase in the abundance of insect larvae and dipterans, but a decrease in the number of earthworms and enchytraeids. Microbial biomass, soil respiration and the nutrients Mg, K and P increased with the amount of LPM supplied to the soil. When analysing the effects of adding large volumes of water via the LPM, results showed that application did not originate significant effects on the parameters measured. The differences obtained when comparing both treatments were mainly attributed to the organic load brought by the LPM and not to the amount of water without LPM.

Placing arbuscular mycorrhizal fungi on the risk assessment test battery of plant protection products (PPPs).

Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts considered a key group in soil systems involved in the provision of several ecosystem services. Recently they have been listed by EFSA as organisms to be included in the test battery for the risk assessment of plant protection product (PPPs). This study aimed to contribute to improve the ISO Protocol (ISO 10832: 2009) by assessing the feasibility of using other AMF species under different test conditions. Overall, results showed that AMF species Gigaspora albida and Rhizophagus clarus (selected out of five AMF species) are suitable to be used in spore germination tests using the ISO protocol (14 days incubation with sand or artificial soil as substrate) to test PPPs. However, several modifications to the protocol were made in order to accommodate the use of the tested isolates, namely the incubation temperature (28 °C instead of 24 °C) and the change of reference substance (boric acid instead of cadmium nitrate). The need for these changes, plus the results obtained with the three fungicides tested (chlorothalonil, mancozeb and metalaxyl-M) and comparisons made with literature on the relevance of the origin of AMF isolates in dictating the adequate test conditions, emphasize the importance of adjusting test conditions (AMF species/isolates and test temperature) when assessing effects for prospective risk assessment targeting different climatic zones. So, further studies should be conducted with different AMF species and isolates from different climatic regions, in order to better define which species/isolate and test conditions should be used to assess effects of a particular PPP targeting a given climatic zone.

Boric acid as reference substance for ecotoxicity tests in tropical artificial soil.

Reference substances are recommended to evaluate the quality of laboratory test species and the reliability of ecotoxicity data. Boric acid (BA) has been recommended as reference substance in some standardized tests in OECD soil, but no data are available for Tropical Artificial Soil (TAS). For this purpose, avoidance tests with Eisenia andrei, lethality tests with E. andrei and Folsomia candida, and reproduction tests with E. andrei, Enchytraeus crypticus and F. candida were carried out in TAS (5% organic matter), following ISO guidelines, and compared between two laboratories. Collembolans were more sensitive than earthworms in lethality tests (LC50 = 342 and > 1000 mg kg-1, respectively). For both laboratories, the EC50 values were similar for reproduction of oligochaeta species (165 mg kg-1 for E. crypticus; 242 and 281 mg kg-1 for E. andrei), but significantly different for reproduction of F. candida (96 and 198 mg kg-1). Present results suggest that boric acid could replace the current pesticides recommended by ISO guidelines as reference substances on reproduction tests with soil invertebrates in TAS. Concerning avoidance tests, additional investigations should be performed with other substances that cause no neurotoxic effects on soil organisms.

An alternative risk assessment framework for tropical soil multi-metal contamination using arbuscular mycorrhizal fungi.

Arbuscular mycorrhizal fungi (AMF) are a key group of soil organisms involved in several ecosystem services, but they had not been explored in retrospective ecological risk assessment (ERA) schemes, partially due to a lack of experimental protocols. We aimed to perform a site-specific test to assess the effects of multiple metal contaminated soil (Zn, Cu, Cd, and Pb) on several ecotypes of AMF and evaluate the conceptual fitness of the performed AMF test to include in the TRIAD approach of ERA schemes. The results demonstrated that increasing metal contaminated soil proportions that inhibited 50 % (IC50) of spore germination varied from 28 to >80. Ecotypes such as Claroideoglomus etunicatum (IC50 > 80) and Racocetra gregaria (IC50 > 80) experienced 50 % reduction in spore germination at metals concentrations of 10,776.3 for Zn, 1015.2 Cu, 65.5 Cd, 140.2 mg dm-3 Pb, that are 3 times higher than those for Acaulospora mellea CMM101 (IC50 28 [16.2-39.8]) (3441.7 Zn, 333.9 Cu, 17.8 Cd, 56.5 mg dm-3 Pb). In the evaluation of the suitability of the AMF ecotoxicological test to ERA, both spore germination and germinative tube growth were best evaluated and thus suitable in the following descending order: Tier III, Tier II, and Tier I. Variable effects of multiple-metal contamination on the ecotypes indicates how AMF community is affected in its pre-symbiotic structures. The ecotoxicological test allowed the selection of two species with the greatest sensitivity (Ambispora appendicula and Rhizophagus clarus CMM103) to the metal matrix, with the potential to best fit ERA objectives. The site-specific ecotoxicological test with AMF ex-situ proved adequate as an alternative test for Tiers II and III of TRIAD ERA schemes for metal contaminated areas. Data generated through test results, such as the inhibition concentrations (ICs), could be incorporated into ERAs risk indexes, increasing its ecological relevance, and reducing overall uncertainties.

Ecotoxicological effects of untreated pig manure from diets with or without growth-promoting supplements on Eisenia andrei in subtropical soils.

This study aimed to evaluate the effects of untreated pig manure from diets incorporating growth-promoting supplements (antibiotics and Zn oxide) on the survival and reproduction of Eisenia andrei earthworms. The tested manures were obtained from four different groups of pigs fed with four different diets: CS, a diet based on corn and soymeal; TR, a diet based on corn, soymeal, and ground wheat (15%); CSa, a diet based on corn and soymeal + 100 ppm of doxycycline + 50 ppm of colistin + 2500 ppm of Zn oxide; and TRa, a diet based on corn, soymeal, and ground wheat (15%) + 100 ppm of doxycycline + 50 ppm of colistin + 2500 ppm of Zn oxide. The study used two soils representative of the Southern region of Brazil (Oxisol and Entisol). In general, there were no significant differences between the different manures tested in each soil. However, there were differences in the toxicity manure on E. andrei between the soils, and the magnitude of this effect was dependent on the applied dose. In Oxisol, LC50 values were higher than 80 m3 ha-1, and EC50 varied from 9 to 27 m3 ha-1. In Entisol, the LC50 values were below the lowest dose tested (< 25 m3 ha-1), and EC50 remained around 5 m3 ha-1. It may be possible that the effects observed were attributed to an excess of nitrogen, copper, and zinc, promoted by the addition of the untreated manure and how these factors interacted with soil type.

Increasing level of liquid pig manure reduces Eisenia andrei and Enchytraeus crypticus reproduction in subtropical soils.

Wastes generated in pig production are widely used as agricultural fertilizers. Nevertheless, such form of disposal supplies large amounts of waste in soils annually and can cause environmental pollution. The ecological risk of this practice to soil organisms has received little attention. Ecotoxicological tests are used to evaluate the toxicity of contaminants added to the soil biota. The aimed to evaluate the effect of liquid pig manure (LPM) on the reproduction of Eisenia andrei and Enchytraeus crypticus when applied in natural soils. LPM doses caused effects on earthworm reproduction in both soils, with EC50 of 112 and 150 m3 ha-1 in the Entisol and Nitosol, respectively. On enchytraeids, LPM had bigger effects, leading to EC50 of 17.7 and 45.0 m3 ha-1 in the Entisol and Nitosol, respectively. The results emphasize the importance to consider the ecological risks of LPM of conducting studies with natural soils and edaphic fauna as indicators.

The fungicide mancozeb affects soil invertebrates in two subtropical Brazilian soils.

Mancozeb is a dithiocarbamate non-systemic fungicide widely used to control fungal diseases of plants, commonly applied in apple orchards in Brazil. Instead of its common use, there are no reports about the risk to non-target organisms in Brazilian soils. We studied the risk of Mancozeb (in the commercial formulation Dithane® NT) for standard invertebrate species (Folsomia candida, Eisenia andrei and Enchytraeus crypticus) in two subtropical Brazilian soils, Oxisol and Ultisol, which are representative of apple production areas in Brazil. Reproduction and survival tests were carried out following ISO guidelines. Results showed that Mancozeb in Oxisol reduced the survival and reproduction of collembolans (LC50 54.43 and EC50 2.72 mg a.i. kg-1) and enchytraeids (LC50 6.97 and EC50 3.56 mg a.i. kg-1), in lowest values than those observed in Ultisol (F. candida LC50 > 1000 and EC50 > 100 mg a.i. kg-1; E. crypticus LC50 280.21 and EC50 29.67). Effects to E. andrei were similar in both soils and indicated a lower sensitivity of this species to Mancozeb. The species F. candida and E. crypticus were more sensitive than E. andrei. These results reinforce the need to include other soil organisms besides earthworms, using chronical endpoints and considering different types of soils, to better predict the risk of pesticides for subtropical soils.

Associative diazotrophic bacteria in grass roots and soils from heavy metal contaminated sites.

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.

Ecotoxicological effects of pig manure on Folsomia candida in subtropical Brazilian soils.

The effects of pig manure, from diets incorporating veterinary pharmaceuticals, on survival and reproduction of Folsomia candida were evaluated. Manures derived from the following diets: corn and soymeal (CS); 85% CS diet+15% wheat meal (TR); CS diet+100ppm doxycycline+50ppm colistin+2500ppm Zn oxide (CSa); TR diet+100ppm doxycycline+50ppm colistin+2500ppm Zn oxide (TRa). Manures were tested in two subtropical soils representative of southern (Oxisol and Entisol). Despite the antibiotics no significant differences were found between the four manures within each soil. However, strong differences were found on the toxicity between soils. In Oxisol, LC50 values were around 100m(3)ha(-1), and EC50 values around 80m(3)ha(-1). In Entisol these were much lower, with LC50 values oscillating around 20m(3)ha(-1) and EC50 values between 10-15m(3)ha(-1). The observed toxicity on both soils was attributed to excess of nitrogen, Cu and Zn in the highest doses. The strong difference between soils could be explained by soil properties, namely CEC, organic matter, and clay contents that were lower in Entisol, indicating a poor ability to retain contaminants increasing their availability in soil. Results suggest that the application of these residues should be regulated not only using a volume-based criterion, but should incorporate data on soil properties, complemented by an ecotoxicological assessment.

Influência de diferentes sistemas de manejo e calagem em experimento de longa duração sobre fungos micorrízicos arbusculares / Influence of different management systems and liming on mycorrhizal arbuscular fungi in a long-term experiment

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.

Associative diazotrophic bacteria in grass roots and soils from heavy metal contaminated sites

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.

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.

Effect of inoculation associated to leaf sprayed Co+Mo on the yield and grain nutrients in common bean (Phaseolus vulgaris L)

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.

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.