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The aim of this research was to evaluate the capacity of symbiotic efficiency of native rhizobia from soils of the state of Rio Grande do Sul (RS), Brazil in Phaseolus lunatus L. plants. Soil and nodule samples from predominant legume plants such as Desmodium species were collected in seven locations of the state of RS. For the isolation of the rhizobia from the soil samples, lima bean “olho de cabra preto” variety and “leucena” (Leucena leucocephala) and plants were used as baits. Subsequently, the symbiotic characterization of the isolates was performed by inoculation on lima bean plants in vitro conditions. The selected bacterial isolates were evaluated for biological nitrogen fixation efficiency in a greenhouse experiment, being determined after: shoot dry mass, root dry mass, nodule dry mass, nitrogen (N) accumulated shoot and calculated the N fixation relative efficiency index. Among the 28 rhizobia isolates tested, 11 induced nodule formation in lima bean. The rhizobia Plu03 and Plu14 stimulated a greater increase of plant dry mass, nodule dry mass and nitrogen accumulation in the shoot, reflecting in a higher relative efficiency index. These results suggest that the isolates Plu03 and Plu14 are more efficient in promoting growth of lima bean, which could be recommended for future agronomic efficiency studies. Key words: Rhizobia, lima bean, biological nitrogen fixation.

Using techniques of inoculation and co-inoculation of plant growth-promoting rhizobacteria (PGPR) could be an alternative with great potential for the wheat agricultural market, aiming towards a higher fertilizer efficiency and a subsequent reduction in environmental impacts. The objective of this study was to evaluate the efficiency of rhizobia symbiont inoculants isolated from legumes, individually and combined with Azospirillum brasilense, in promoting the growth of the wheat crop. The experiments were performed with the cultivars BRS Parrudo and TBIO Sossego, both inoculated and co-inoculated with the rhizobia UFRGS Vp16 and UFRGS Lc348, and A. brasilense, and under nitrogen dosage levels recommended for wheat plants. Inoculation of rhizobia, isolated or combined with A. brasilense, promotes increases in the production of wheat grains with half of the nitrogen dose recommended in the two evaluated cultivars, standing as an economically viable and ecologically sustainable alternative for the agricultural market.

Most studies evaluating the effects of grazing intensities on soils in Brazilian grasslands have focused on abiotic parameters, especially chemical or physical properties. In this context, soil arthropods have been largely unexplored, especially Collembola. This research addressed the effect of different grazing intensities on the composition and structure (abundance, richness, diversity, and evenness) of Collembola communities under different grazing intensity levels. Collembola were collected at different cattle grazing intensity level treatments (high, moderate, and low) in southern Brazilian native grasslands (also known as Campos). Our findings indicated significant changes in the composition of Collembola communities through grazing intensities. The treatment with the lowest grazing intensity was found to be substantially different from all others, probably because of a high abundance of some taxa (i.e. Entomobrya spp). We also observed that morphospecies richness and diversity tended to peak at moderate grazing intensities, whereas total abundance was higher in the lowest grazing intensity treatment. This study provides experimental evidence that disturbances caused by cattle grazing in native grasslands might impact soil faunal communities: increases in grazing intensity affected soil arthropod composition and structure by reducing their abundance, richness and diversity. It is important to highlight taxonomical richness and diversity as an intrinsic characteristic of communities insuring their functionality as a consequence of niche occupation and complementarity.

Although inoculating soybean with rhizobia for biological nitrogen fixation is a common practice in agriculture, rhizobia are also known to associate with grasses. In this study, we evaluate the potential utility of the rhizobial strains SEMIA 587 and 5019 (Bradyrhizobium elkanii), 5079 (Bradyrhizobium japonicum), and 5080 (Bradyrhizobium diazoefficiens), recommended for Brazilian soybean inoculation, in colonizing black oat plants and promoting growth in black and white oats, and ryegrass. Inoculation of white oats with SEMIA 587 increase the seed germination (SG) by 32.09%, whereas the SG of black oats inoculated with SEMIA 587 and 5019 increased by 40.38% and 37.85%, respectively. Similarly, inoculation of ryegrass with all strains increased SG values between 24.63 and 27.59%. In addition, white oats with SEMIA 587 and 5080 had root areas significantly superior to those in other treatments, whereas inoculation with SEMIA 5079 and 5080 resulted in the highest volume of roots. Likewise, SEMIA 5079 and 5080 significantly increased the length, volume, and area of black oats roots, whereas SEMIA 587 increased the volume, area, and dry mass of roots and shoot. Inoculation in ryegrass with SEMIA 587 significantly increased the root volume. Moreover, most strains transformed with gfp and gus were observed to colonize the roots of black oats. Collectively, the findings of this study indicate that rhizobial strains recommended for inoculation of soybean can also be used to promote the growth of the three assessed grass species, and are able to colonize the roots of black oats.

International audience; Background and aimsInteractions between functional groups of soil fauna and plants are poorly explored although they drive functional processes such as nutrient availability and therefore plant performance. Here, we investigated the separated and combined effects of two collembolan functional groups on soil properties and growth of Lolium perenne, a typical grass species from temperate grasslands.MethodsUnder microcosm conditions, we established four treatments based on the presence and combination of two collembolan functional groups: (1) control without Collembola; (2) epedaphic species; (3) euedaphic species; (4) epedaphic + euedaphic species. After five months of experiment, we measured the effect of those treatments on both nutritional and morphological variables of L. perenne and on soil properties.ResultsCollembolan presence stimulated plant performance. Individuals of L. perenne growing with euedaphic species presented higher numbers of leaves and nutrient contents compared with individuals growing with epedaphic species. Further, the combination of both collembolan functional groups enhanced plant performance and soil nutrient availability, demonstrating that a functionally diversified soil fauna assemblage cause overyielding of ecological processes.ConclusionOur results provide evidences of complementarity interactions between different functional groups of soil fauna causing overyielding of primary production.

The Adesmia species found in Rio Grande do Sul and Santa Catarina have high nutritional quality and may be used in breeding programs of native grasslands. The aim of this study was to evaluate the growth promotion in Adesmia species by rhizobacteria producing indolyl acetic acid (IAA). Seven isolates of bacteria from nodules of Adesmia latifoliafrom the Epagri collection of rhizobacteria were used. These were analyzed for production of indolyl acetic acid and promotion of plant growth in A. latifolia, A. psoraleoides, A. riograndensis and A. tristis. The results showed a variable production of IAA by different isolates used. The isolates produced different effects in promoting the growth of different species of Adesmia. The bacterial strains used are specific for nodulation in A. latifolia. Leaf number and length of twoleaved shoots are not affected by the isolates used in this study. The effects of bacteria isolated from nodules in promoting growth varied depending on the interaction with the different species of Adesmia. EEL0710 strain promotes increased growth in A. latifolia, A. psoraleoides and A. tristis. EEL1710A strain promotes increased growth in A. riograndensis. Thelevel of endogenous IAA has no direct relationship in promoting the growth of Adesmia species. As espécies de Adesmia encontradas no Rio Grande do Sul e em Santa Catarina apresentam alta qualidade forrageira e podem ser utilizadas em programas de melhoramento de campos nativos. O objetivo deste trabalho foi avaliar a promoção do crescimento em espécies de adésmia por rizobactérias produtoras de ácido indolacético (AIA). Foram utilizados sete isolados de bactérias de nódulos de adésmia e pertencentes à coleção de rizobactérias da Epagri. Avaliaram-se a produção de AIA in vitro e a promoção de crescimento vegetal pelos isolados em Adesmia latifolia, A. psoraleoides, A. riograndensis e A. tristis. Os isolados bacterianos utilizados são específicos para nodulação em A. latifolia.Os resultados obtidos demonstraram uma produção variável de AIA pelos diferentes isolados. O número de folhas bifoliadas e o comprimento dos brotos não são afetados pelos isolados utilizados neste trabalho. Os efeitos dos isolados de bactérias de nódulos na promoção do crescimento variaram em função da interação com as diferentes espécies deadésmia. O isolado EEL0710 promove maior crescimento em Adesmia latifolia, A. psoraleoides e A. tristis. O isolado EEL1710Apromove maior crescimento em A. riograndensis. O nível endógeno de ácido indolacético não apresenta uma relação direta na promoção do crescimento das espécies de Adesmia

Aiming at obtaining high productivity and reduction of production costs, new techniques have been studied in rice crops, such as the use of plant growth promoting rhizobacteria (PGPR). The objective of this study was to evaluate the efficiency of inoculation and co-inoculation of rhizobia and Azospirillum brasilense in promoting the growth of irrigated rice plants cultivated in the field. Two experiments were conducted in the field, in the 2014/15 and 2015/16 crops, at the Rio Grande do Sul Rice Experiment Station. The experiment was composed of seven treatments, with two control treatments, without inoculation (81 kg ha-1 N and 135 kg ha-1 N, equivalent to 60% and 100%, respectively, of the recommended nitrogen dose). The other five treatments received only 60% of the N dose and were inoculated with the UFRGS Vp16 (Burkholderia sp.) and UFRGS Lc348 (Mesorhizobium sp.) Rhizobia, and with the commercial product containing the A. brasilense AbV5 and AbV6 strains. Inoculation and co-inoculation with PGPR may represent a viable alternative to reduce the amount of nitrogen fertilizers in rice crops.

The soil is the most important carbon reservoir, but agricultural practices involved in tillage systems decrease the soil carbon stock. This study aims to evaluate the effect of no-tillage (NT) on carbon and microbiological attributes of the soil in corn plantations in Manaus-AM, Brazil. Soil was sampled in a secondary forest (SF) and in corn grown under different tillage systems, including conventional tillage (CT), which makes use of plowing and harrowing operations, and no-tillage (NT). Soil variables studied included, carbon content, soil microbial carbon and basal respiration, metabolic and microbial quotients. The data were analyzed by analysis of variance and Tukey's test. The results demonstrated that NT resulted higher carbon, lower basal respiration, and lower metabolic quotient than CT and SF. However, soil microbial carbon was similar in all tillage systems studied. We conclude that NT corn cropping increased soil carbon content more than CT, while it decreased basal respiration and metabolic quotient when compared to NT and SF. Moreover, soil microbial biomass in corn was similar in all tillage systems studied. This research demonstrated the importance of NT to soil carbon conservation and soil management in corn cropping. Key words: Tillage systems, land use, microbial soil biomass, basal respiration.

Rhizobia are able to increase yield of non-leguminous species through production of phyto-stimulating substances. This study aimed to evaluate the inoculation effect of rhizobia UFRGS Lc348 and VP16 on millet and Sudan grass yield and germination, and verify the enrichment effect of culture medium with tryptophan, which leads on the rhizobium/plant interaction. Experiments in vitro and greenhouse conditions were conducted. In millet, the inoculation with VP16 grown in culture medium with or without tryptophan induces greater length of hypocotyl and epicotyl under in vitro conditions. UFRGS Lc348 treatment induces longer hypocotyls of millet under in vitro conditions. No effects were observed with the millet inoculation in greenhouse. In Sudan grass, inoculation with VP16 enriched with tryptophan increased dry matter in shoots of adult plants. In millet seedlings had achieved an increasing in elongation in vitro conditions, which could represent an adaptive advantage in the search for water and nutrients in the rhizospheric environment during the initial growth of millet. Similarly, if verified in field conditions, Sudan grass had achieved an increasing in greenhouse conditions with the inoculation of tryptophan-enriched VP16, which could be correlated with a significant gain in crop yield. Therefore, these relationships between tryptophan-enriched VP16 and Sudan grass should be verified in subsequent studies under field conditions. Rizobios son capaces de influir en el rendimiento de las especies no leguminosas través de la producción de sustancias fitoestimulantes. El objetivo de este estudio fue el de estudiar el efecto de la inoculación de rizobios UFRGS Lc348 y VP16 sobre la germinación y el rendimiento de millo y pasto Sudán, así como verificar si el enriquecimiento del medio de cultivo con triptófano interfiere en la interacción rizobio/planta. Para este fin se llevaron a cabo experimentos in vitro y bajo condiciones de invernadero. En el experimento con millo en condiciones in vitro, la inoculación con VP16 cultivado en medio enriquecido o no enriquecido con triptófano induce una mayor extensión de hipocótilo y epicótilo. El tratamiento UFRGS Lc348 induce una mayor extensión de hipocótilo en plantas de millo. En plantas adultas de millo no hubo efecto de la inoculación. En pasto Sudán, la inoculación de VP16 enriquecida con triptófano aumentó la masa seca de las plantas adultas. Los aumentos de elongación de plántulas de millo en condiciones in vitro pueden representar una ventaja adaptativa en la búsqueda de agua y nutrientes en el ambiente rizosférico durante el crecimiento inicial del millo. De manera similar, si se verifica en condiciones de campo, el incremento de pasto Sudán observado en condiciones de invernadero con la inoculación de VP16 enriquecido con triptófano, esto puede significar una ganancia significativa en el rendimiento del cultivo. Por lo tanto, estas relaciones entre VP16 enriquecido con triptófano y pasto Sudán deben ser verificadas en estudios posteriores en condiciones de campo.

The two main bottlenecks for a successful phytoremediation program are the metal availability in soil and the metal uptake and transfer to shoots of high biomass plants. Several agronomical practices have been tested to boost the bioavailability of metals in soils and accumulation in plants. Here we assessed the feasibility of plant-growth-promoting bacteria (PGPB) isolated from a site contaminated by gold ore processing activities to assist the phytoremediation of As, Cd, and Pb by Sorghum bicolor and mitigate the metal toxicity in plants. The bacteria Kluyvera intermedia, Klebsiella oxytoca, and Citrobacter murliniae were evaluated in single, double, and triple inoculations. They are regarded as metal resistant and were isolated from the rhizosphere of species naturally growing on the metal contaminated site. The treatments comprised two soils (contaminated and non-contaminated) and single (K. intermedia, K. oxytoca, or C. murliniae) or multiple inoculations (K. intermedia + K. oxytoca; K. intermedia + C. murliniae; K. oxytoca + C. murliniae; K. intermedia + K. oxytoca + C. murliniae). Plants were grown for 42 days after inoculation. The results showed that the PGPB K. oxytoca and the combination of K. intermedia + K. oxytoca and K. intermedia + C. murliniae were able to mitigate the metal toxicity in the contaminated soil and hence increase the shoot biomass, with implications to the effectiveness of phytoextraction. The sorghum ability to translocate Cd to shoots in the contaminated soil was enhanced through the single inoculation with K. oxytoca, C. murliniae, and K. oxytoca, as well as by the joint-inoculation with K. oxytoca + C. murliniae, and K. intermedia + K. oxytoca + C. murliniae. Higher accumulation of metals in shoots is a crucial factor in successful phytoextraction. Arsenic and Pb, on the other hand, had their uptake and concentration in roots stimulated by the inoculation. Therefore, regarding these two metals, phytostabilization programs could benefit from the use of the bacteria studied here.

Land-use change has been identified, among global changes, as the main threat causing biodiversity loss, locally and regionally. This is especially true in Southern Brazil with the two main biomes (Pampa and Atlantic forest) facing high conversion rate into agricultural land to meet increasing demand for food and fuel. Within this region, we focused on epigeic biota across three land-use types (forest, grassland and Eucalyptus plantation). We used both a taxonomical and a trait-based approach to depict the changes of Epigeic Collembola assemblages across land-use types. Furthermore, we tested trait-convergence and trait-divergence across land-use types to infer how the environmental filtering and biotic interactions can affect assembly rules and collembolan community composition. Results differed according to the approach used (either taxonomical or trait-based). In general, diversity indices based on the taxonomical approach did not significantly differ between forest and grassland, whereas Eucalyptus plantation showed significantly lower values. Functional diversity was significantly higher in forest and similar between grassland and Eucalyptus plantation. Furthermore, we found both convergence and divergence of subsets of traits related to the land-use types. The trait-convergence tended to be higher in grassland sites and rather linked to sensorial traits (number of ocelli, antenna length, and trichobothria), drought tolerance traits (body size) and habitat preference traits (pigmentation level, furca development, scale, number of ocelli, antenna length, and body size). On the opposite, Trait-divergence was only linked to sensorial traits (antenna length and postantennal organ) and greatest in forest sites. Our findings showed that a trait-based approach associated with a taxonomic one provides a better understanding of the collembolan community structuring in response to biotic and abiotic changes across different land-use types.

ability to associate symbiotically with rhizobia. The objective of this study was to isolate, authenticate and select effective rhizobia obtained from native serradella (Ornithopus micranthus) to reduce the need for mineral fertilizer. Nodules, roots of serradella and rhizosphere soil samples were collected in seven municipalities from Rio Grande do Sul and Santa Catarina states. Bacterial colonies were isolated and identified based on morphological characteristics. The authentification and initial selection of rhizobia were conducted in vitro. The most promising strains from the in vitro study were evaluated in a greenhouse experiment for 60 days. Among the 148 bacterial cultures characterized, 113 induced the formation of nodules in serradella while 32 isolate effectively increased fresh mass of plants under in vitro conditions. The strains UFRGS Om57, UFRGS Om59 and UFRGS Om148 formed nodules with greater dry mass and produced high dry mass of plants (shoots and roots) which allowed greater accumulation of N in the shoots. Key words: Plant growth promoting rhizobacteria (PGPR); biological fixation of nitrogen; Ornithopus micrantus; pasture.

Phytoremediation consists of biological techniques for heavy metal remediation, which include exploring the genetic package of vegetable species to remove heavy metals from the environment. The goals of this study were to investigate heavy metal and bioaugmentation effects on growth and nutrient uptake by Mucuna deeringiana; to determine the metal translocation factor and bioconcentration factor and provide insight for using native bacteria to enhance heavy metal accumulation. The experiment was conducted under greenhouse conditions using a 2 × 4 factorial scheme with highly and slightly contaminated soil samples and inoculating M. deeringiana with three highly lead (Pb+2)-resistant bacteria Kluyvera intermedia (Ki), Klebsiella oxytoca (Ko), and Citrobacter murliniae (Cm) isolated from the rhizosphere of native plants identified as Senecio brasiliensis (Spreng.) Less., Senecio leptolobus DC., and Baccharis trimera (Less) DC., respectively. The increased heavy metal concentrations in soil samples do not decrease the root dry mass of M. deeringiana, concerning the number and dry weight of nodules. The shoot dry mass is reduced by the increasing concentration of heavy metals in soil associated with Kluyvera intermedia and Klebsiella oxytoca bacteria. The number of nodules is affected by heavy metals associated with Citrobacter murliniae bacteria. The bacteria K. intermedia, C. murliniae, and K. oxytoca increase the lead and cadmium available in the soil and enhanced metal uptake by Mucuna deeringiana. The M. deeringiana specie has characteristics that make it hyperaccumulate copper and zinc. The translocation and bioconcentration factors for M. deeringiana characterize it as a promising candidate to phytostabilize multi-metal contaminated soils.

Different soil management in crop cultures like maize can produce a variety of effects on soil fauna. Conventional cropping includes soil tillage, promoting organic matter losses and destruction of soil structure, whereas no-tillage cropping includes a herbicide application which can potentially affect soil fauna. In both management systems, insecticides are often used, such as pyrethroid insecticides, to prevent insect pests. Understanding the impact of these different cropping systems in their different phases on soil mesofauna and investigating the ability of soil communities to recover may provide important information to select cropping strategies which are more protective of soil biodiversity. With this aim, a terrestrial model ecosystem experiment was performed over eighty-nine days. The test treatments, all including maize, were: undisturbed soil; conventional tillage; conventional tillage with insecticide; no-tillage soil with herbicide; no-tillage soil with herbicide and insecticide. In each TME, soil samples from 0 to 5 and 5-10 cm of the top layer were collected from which collembolans and mites were identified to species, genus or subfamily level, and enchytraeid abundance was determined. Soil tillage did not affect soil communities, but insecticide application did. For collembolans and enchytraeids, the impact of the insecticide was independent of soil management, but for mites, insecticide impact was longer in conventional tillage than in no-tillage system. Changes on collembolan abundance, in general, did not promote changes in mean community trait values and functional diversity. Data suggest that no-tillage management is more protective to soil fauna than conventional tillage.

Made available in DSpace on 2018-11-26T17:48:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01. Added 1 bitstream(s) on 2019-10-09T18:27:24Z : No. of bitstreams: 1 S0100-06832018000100514.pdf: 290304 bytes, checksum: 0ff8739ab4a154929cbb4d4f969361e3 (MD5) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) There is a complex interaction between various components of the soil ecosystem, including microbial biomass and soil chemical contaminants such as heavy metals and radionuclides, which may greatly affect the efficiency of bioremediation techniques. The aim of this study was to investigate microbial capacity to change pH, changes in the metal soluble-exchangeable fraction, and effects of initial heavy metal contents on soil samples in microbial solubilization/immobilization capacity. The soil samples used in this study were collected at a known metal-contaminated site. Three highly metal-resistant bacteria were isolated from rhizosphere soil samples collected on weed species identified as Senecio brasiliensis, Senecio leptolobus, and Baccharis trimera. A completely randomized experimental design in a factorial arrangement was used, with three replicates. In general, with an acid pH, the isolates neutralized the contaminated growth media. In a neutral or basic initial pH, increases in pH were observed in the media, so these bacteria have an alkalizing effect on the growth media. Soluble metal contents were quite different and depend on the microbial species and heavy metal contents in the soil samples. The soluble-exchangeable fraction of metal such as Cu, Zn, Ni, Cr, Cd, Pb, and Ba may be unavailable after inoculation with heavy metal resistant rhizobacteria. A promising approach seems to be the application of inoculants with metal-resistant bacteria in bioremediation of multi-metal-polluted environments to improve the efficiency of this environmentally friendly technology. Univ Fed Piaui, Campus Cinobelina Elvas, Bom Jesus, Piaui, Brazil Univ Fed Rio Grande do Sul, Dept Solos, Porto Alegre, RS, Brazil Univ Estadual Paulista, Inst Biociencias Rio Claro, Programa Posgrad Ciencias Biol, Rio Claro, SP, Brazil Univ Fed Piaui, Programa Posgrad Solos & Nutr Plantas, Campus Cinobelina Elvas, Bom Jesus, Piaui, Brazil Inst Rio Grandense Arroz, Porto Alegre, RS, Brazil Univ Estadual Paulista, Inst Biociencias Rio Claro, Programa Posgrad Ciencias Biol, Rio Claro, SP, Brazil

Seed inoculation with plant growth promoting rhizobacteria (PGPR) is an ideal tool to supply the soil with a high density of beneficial microorganisms. However, maintaining viable microorganisms is a major problem during seed treatment and storage. In this work, an evaluation was made of the effect of bacterial immobilization in nanofibers on the stability (viability and maintenance of beneficial properties) of two potential PGPR, Pantoea agglomerans ISIB55 and Burkholderia caribensis ISIB40. Moreover, the impact of soybean seed coating with nanofiber-immobilized rhizobacteria on bacterial survival during seed storage and on germination and plant growth parameters was determined. Bacterial nanoimmobilization and subsequent seed coating with nanofiber-immobilized rhizobacteria were carried out by electrospinning. The results demonstrate that this technique successfully immobilized P. agglomerans ISIB55 and B. caribensis ISIB40 because it did not affect the viability or beneficial properties of either rhizobacteria. Seed coating with nanofiber-immobilized rhizobacteria improved P. agglomerans ISIB55 and B. caribensis ISIB40 survival on seeds stored for 30 days and contributed to the successful colonization of both bacteria on the plant root. Moreover, seed coating with P. agglomerans ISIB55 increased germination, length and dry weight of the root. Furthermore, seed coating with B. caribensis ISIB40 increased leaf number and dry weight of the shoot. Therefore, the technique applied in the present work to coat seeds with nanofiber-immobilized PGPR could be considered a promising eco-friendly approach to improve soybean production using a microbial inoculant. Fil: de Gregorio, Priscilla Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina Fil: Michavila, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina Fil: Ricciardi Muller, Lenise. Tecnano Produtos e Serviços Ltda; Brasil Fil: Borges, Clarissa de Souza. Universidade Federal do Rio Grande do Sul; Brasil Fil: Pomares, Maria Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina Fil: Sá, Enilson Luiz Saccol de. Universidade Federal do Rio Grande do Sul; Brasil Fil: Pereira, Claudio. Tecnano Produtos e Serviços Ltda; Brasil Fil: Vincent, Paula Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; Argentina

The electrospinning technique of rhizobia immobilization in nanofibres is an innovative and promising alternative for reducing the harmful effects of environmental stress on bacteria strains in a possible inoculant nanotechnology product for use in agriculture. The use of polyvinyl alcohol (PVA) shows up as an effective polymer in cell encapsulation because of its physical characteristics, such as viscosity and power of scattering. The aim of these studies has been to evaluate the survival of rhizobia incorporated in PVA nanofibres, which were applied to soybean seed and then subjected to different storage times and exposure to fungicide. The maintenance of the symbiotic characteristics of the incorporated bacterial strains was also evaluated, noting the formation of nodules in the soybean seedlings. No significant differences in the cell survival at 0 h and after 24 h of storage were observed. After 48 h, a significant difference in the bacterial cell concentration of the seeds affixed with PVA nanofibres was observed. Exposure to the fungicide decreased the viability of the bacteria strains even when coated with the nanofibres. A larger number of nodules formed in soybean seedlings from seeds inoculated with rhizobia incorporated in PVA nanofibres than from seeds inoculated with rhizobia without PVA. Thus, the electrospinning technique is a great alternative to the usual protector inoculants because of its unprecedented capacity to control the release of bacteria.

Rhizobia and associative bacteria promote growth in rice plants (Oryza sativa L.) through a series of mechanisms, but most studies on inoculation have been performed based on inoculation with these bacteria in a separate or singular manner. The objective of this study was to assess the efficiency of single/isolated inoculation and inoculation combined with symbiotic rhizobia from forage legume and with Azospirillum brasilense on promoting growth and the root colonization process in wetland rice. Two rhizobia among four isolates from a greenhouse and a laboratory experiment were selected that efficiently promoted seed germination and rice plant growth in a sterilized substrate and in soil. The two most efficient isolates (UFRGS Vp16 and UFRGS Lc348) were inoculated alone or in combination with a commercial product containing A. brasilense in two field experiments using two wetland rice cultivars over two growing seasons. In the field experiments, these isolates coinoculated with A. brasilense promoted larger increases in the agronomic variables of wetland rice compared to the control without inoculation. Confocal laser microscopy confirmed the presence of inoculated bacteria tagged with gfp (UFRGS Vp16, UFRGS Lc348, and A. brasilense) colonizing the root surface of the rice seedlings, mainly in the root hairs and lateral roots.

Due to their ecologic and economic importance, bradyrhizobia have been extensively studied in recent years. Since 1992, Bradyrhizobium elkanii SEMIA 587 and SEMIA 5019 and Bradyrhizobium japonicum SEMIA 5079 and SEMIA 5080 have been widely used in most Brazilian soybean fields. The objective of this work was to estimate the genetic variability of bradyrhizobial isolates recovered from soils under rhizobial inoculation and different soil managements. Only 25% of the isolates demonstrated high similarities to the original strains, and a strong correlation was obtained between the bradyrhizobial genetic variability and soil management. A high level of genetic diversity was observed both within isolates (H = 5.46) as well as among the different soil practices. Soil under no-tillage presented a higher bradyrhizobia diversity compared with bradyrhizobia isolated from soil under conventional tillage. Serological characterization also indicated that B. elkanii strains SEMIA 587 and SEMIA 5019 were more competitive and presented a higher nodular occupancy capacity than strains belonging to B. japonicum species in Southern Brazilian soils.

The genetic diversity and symbiotic efficiency among indigenous rhizobia isolates obtained from native field with or without organic fertilization and superficial mineral fertilization were investigated. Eighty-six indigenous rhizobia were isolated from these fields using four common bean varieties as trap-host. The common bean varieties Mexico 309 and Rio Tibagi selected the most efficient rhizobia strains because they showed the best yields and N contents results. The genetic characterization of 36 rhizobia isolates was evaluated by using electrophoretic profiles of amplification products using primers ERIC1-R and ERIC-2. Our results demonstrated that besides the large diversity in the indigenous rhizobial community, the genotype of the trap-host probably influences the selection of the most efficient strains.

The population size of diazotrophic bacteria naturally associated with the maize rhizosphere can be affected by biotic and environmental factors. In this work we have evaluated the effect of two genotypes of maize, with and without nitrogen fertilization, on the population dynamics and distribution of diazotrophic bacteria associated with maize plants over different plant ontogenic stages. The study was carried out in a field experiment with and without nitrogen fertilization, using two maize cultivars (Santa Helena 8447 and Santa Rosa 3063) previously selected from 32 maize cultivars for the lowest and highest response to nitrogen fertilization, respectively. Microbiological and molecular approaches were used to characterize the diazotrophic bacterial population structure. Bacterial population was assessed by the most probable number using semi-solid N-free media, and by DNA isolation from soil and plant tissue followed by amplification of nifH gene fragments using nested PCR, and by RFLP analysis using the restriction endonucleases TaqI and HaeIII. The dynamics of the diazotrophic bacterial population were affected by the ontogenic stage of the maize plants, but not by the cultivar type. Roots were the preferred site of colonization, independent of cultivar type and growth stage. During the first stage of maize growth, addition of nitrogen fertilizer negatively affected the diazotrophic bacterial population.

Anthracene is a polycyclic aromatic hydrocarbon (PAH) that presents a high pollution potential and health risk and has been used as a model for degradation studies on PAHs because of its relative toxicity. This study aimed to evaluate anthracene degradation by Pseudomonas sp. isolated from a 14-year-old petrochemical sludge landfarming site. Three isolates were selected from 26 by the best growth in anthracene and two of them were identified by 16S rRNA gene sequencing as Ps. aeruginosa and Ps. citronellolis . They showed better growth at pH 7.0 and 30 °C in medium containing up to 2 g anthracene L −1 . They were also able to grow in medium containing phenanthrene, pyrene, gasoline and diesel oil. Analysis of anthracene degradation estimated by gas chromatography showed that Ps. aeruginosa isolate 312A had the highest rate of degradation (3.90 mg L −1 day −1 ), degrading 71% of the anthracene added to the medium (250 mg L −1 ) after 48 days. Ps. citronellolis 222A showed an intermediate level of degradation (51%), but Ps. aeruginosa 332C degraded only 24.4%. Isolate 312A was also responsible for the highest phenanthrene and pyrene degradation after 48 days. In order to establish the mechanisms involved in the PAH degradation, surfactant production by the isolates was assessed by an emulsification index and reduction of the surface tension in the mineral medium free of cells. Emulsification was not detected, indicating that the isolates did not produce high molecular weight surfactant, although reduction in surface tension indicated production of low molecular weight surfactant compounds. The medium containing Ps. citronellolis 222A showed the highest reduction in surface tension, which could increase anthracene bioavailability for biodegradation. To our knowledge, this is the first report concerning increase of anthracene degradation by surfactants produced by Ps. citronellolis . However, the highest degradation rate shown by Ps. aeruginosa 312A was not related to surfactant production, indicating that some other mechanism could be involved in anthracene degradation. The Pseudomonas isolates may be useful for the study of PAH degradation and for bioremediation purposes.

O presente trabalho teve como objetivos avaliar a quantidade de nitrogênio imobilizado e a sua remineralização, nos sistemas plantio direto (SPD) e convencional (SC), ao longo do ciclo do milho. Para tal, foram coletadas amostras da camada de 0-5cm de solo semeado com milho em sucessão à aveia preta, sob os sistemas convencional e plantio direto, no dia da semeadura do milho e 46, 62, 88 e 112 dias após. Amostras da parte aérea das plantas de milho foram coletadas nas mesmas épocas, com exceção da primeira, e avaliadas quanto à quantidade de nitrogênio acumulado. As amostras de solo foram avaliadas quanto à quantidade de nitrogênio mineral no solo, de nitrogênio e carbono potencialmente mineralizáveis, atividade de urease e de nitrogênio imobilizado na biomassa microbiana. A imobilização microbiana do nitrogênio foi maior no sistema plantio direto, levando a uma menor quantidade de nitrogênio mineral no solo e resultando em menor acúmulo de nitrogênio na parte aérea do milho ao final do seu ciclo neste sistema, em comparação com o convencional. Não foi observada remineralização do nitrogênio imobilizado, indicando que a biomassa microbiana atuou mais como agente da mineralização de nitrogênio orgânico do que como fonte de nitrogênio potencialmente mineralizável. The present research aimed to evaluate the amount of nitrogen immobilized and its remineralization, in conventional and in no-till systems, during the corn cycle. A soil that was used for oats crop was seeded with corn and subjected to under conventional and no-till systems. Samples were collected from the top (0-5cm) soil layer on the day of the corn seeding and after 46, 62, 88 and 112 days. At the same time, the aerial parts of corn plants were collected and nitrogen accumulation was evaluated. Soil samples were assayed for mineral N, potentially mineralizable N and C, activity and immobilized N. Microbial nitrogen immobilization was higher in no-till system, reducing the soil mineral nitrogen concentration and resulting in a lower amount of nitrogen in the aerial parts of corn plants at the end of the growth cycle. Nitrogen remineralization was not observed, indicating that the microbial biomass acted more as an agent of organic N mineralization than as a source of potentially mineralizable N.

This paper aims to contribute to the discussion and concern on the future of microbiology in Brazil. This work presents a survey carried out in 2001 that shows a picture of Microbiology status in Brazil. Most of the conclusions are based on the data collected from the university courses and from the data supplied by the Brazilian National Research Council (CNPq) and the Coordination for the Improvement of Higher Level Personnel (CAPES). However, some of the affirmatives are more based on the experiences with postgraduate teaching in microbiology than on the data provided by official institutions. Such affirmatives were made in order to improve the development of the microbiology in Brazil. Also, a plan that proposes higher number of scholarships awarded to microbiology, to increase the possibility to form a critical mass necessary for further development of the Brazilian microbiology, is presented in order to produce discussion and more debate on the future of the Microbiology in Brazil.Este artigo visa contribuir para a discussão relacionada ao futuro da microbiologia no Brasil. Este trabalho apresenta um levantamento, realizado em 2001, que mostra um quadro da situação atual da microbiologia no Brasil. A maioria das conclusões são fundamentadas nos dados coletados dos cursos universitários e dos dados fornecidos pelo Conselho Nacional de Pesquisa (CNPq) brasileiro e pela Coordenação para o Aperfeiçoamento de Pessoal de Nível Superior (CAPES). No entanto, algumas das afirmativas são baseadas mais nas experiências de ensino de pós-graduação em microbiologia do que nos dados fornecidos pelas instituições oficiais. Tais afirmativas foram feitas no sentidos de incrementar o desenvolvimento da microbiologia no Brasil. Além disso, é apresentado um plano que propõe maior número de bolsas concedidas para a área de microbiologia, para aumentar a possibilidade de formar uma massa crítica necessária para maior desenvolvimento da microbiologia brasileira, visando produzir discussão e mais debate sobre o futuro da microbiologia no Brasil.

RESUMO: Embora os rizóbios não apresentem a capacidade de fixar nitrogênio em plantas de arroz, estes podem estimular o crescimento da parte aérea e da raiz, aumentando a absorção de nutrientes, como o nitrogênio, e a produtividade. Com o trabalho, avaliou-se o efeito de rizóbios em promover o crescimento de plantas de arroz em função de doses de nitrogênio (N). Efetuou-se um experimento com vasos contendo solo e plantas da cultivar IRGA 424. As plantas foram inoculadas com oito isolados de rizóbios e adubadas com doses equivalentes a 0, 40, 80 e 160kg N ha-1. Avaliou-se a matéria seca e a quantidade de N acumulada na parte aérea e o perfilhamento das plantas. O efeito do N no crescimento de arroz aumentou com a inoculação de rizóbios. A matéria seca da parte aérea das plantas inoculadas e que receberam, aproximadamente, metade da maior dose de N foi equivalente às que receberam a maior dose desse nutriente e sem inoculação. Além disso, a inoculação com rizóbios aumentou o perfilhamento e a absorção de N. A inoculação de rizóbios em arroz, embora não dispense a adubação nitrogenada, tem potencial para aumentar a produção e a eficiência do uso do N. ABSTRACT: Although rhizobia do not show the ability to fix nitrogen in rice plants, they can stimulate shoot and root growth and even increase productivity and also can increase the plant efficiency in the absorption of nutrients such as nitrogen. This study evaluated the effect of rhizobia in promoting the growth of rice plants fertilized with nitrogen (N). An experiment was developed in pots containing soil and rice of the cultivar IRGA 424. The plants were inoculated with eight isolates of rhizobia and fertilized with 0, 40, 80 and 160kg N ha-1. We evaluated the dry matter of shoots, tillering and amounts of N absorbed by the shoots. The effect of N on rice growth increased by inoculation of rhizobia. Inoculated plants and fertilized with approximately half of the higher N dose, produced shoot equivalent of the plants that received the highest dose of this nutrient and without inoculation. Moreover, inoculation with rhizobia increased tillering and absorption of N. The practice of rhizobia inoculation in rice, although not replace the nitrogen fertilization, have great potential for rice farmers, allowing greater production and efficiency of N use.

This work aimed to evaluate the symbiotic compatibility and nodulation efficiency of rhizobia isolated from Desmodium incanum, Lotus corniculatus, L. subbiflorus, L. uliginosus and L. glaber plants by cross-inoculation. Twelve reference strains and 21 native isolates of rhizobia were genetically analyzed by the BOX-PCR technique, which showed a high genetic diversity among the rhizobia studied. The isolates were also characterized based on their production of indolic compounds and siderophores, as well as on their tolerance to salinity. Fifteen of the 33 rhizobia analyzed were able to produce indolic compounds, whereas 13 produced siderophores. All the tested rhizobia were sensitive to high salinity, although some were able to grow in solutions of up to 2% NaCl. Most of the native rhizobia isolated from L. uliginosus were able to induce nodulation in all plant species studied. In a greenhouse experiment using both D. incanum and L. corniculatus plants, the rhizobia isolate UFRGS Lu2 promoted the greatest plant growth. The results demonstrate that there are native rhizobia in the soils of southern Brazil that have low host specificity and are able to induce nodulation and form active nodules in several plant species.

In vitro rooting and the acclimatization of micropropagated rootstocks of apple trees is essential for plant development in the field. The aim of this work was to assess the use of rhizobia of Adesmia latifolia to promote rooting and acclimatization in micropropagated Marubakaido apple rootstock. An experiment involving in vitro rooting and acclimatization was performed with four strains of rhizobium and two controls, one with and the other without the addition of synthetic indoleacetic acid. The inoculated treatments involved the use of sterile inoculum and inoculum containing live rhizobia. The most significant effects on the rooting rate, primary-root length, number of roots, root length, fresh-shoot biomass, and fresh-root biomass were obtained by inoculation with strain EEL16010B and with synthetic indole acetic acid. However, there was no difference in the growth of apple explants in the acclimatization experiments. Strain EEL16010B can be used to induce in vitro rooting of the Marubakaido rootstock and can replace the use of synthetic indoleacetic acid in the rooting of this cultivar.

O cornichão é uma leguminosa forrageira perene hiberno-primaveril de grande importância para o Rio Grande do Sul, destacando-se pela capacidade de se manter em solos relativamente ácidos e pouco férteis. Com este trabalho, objetivou-se a seleção de rizóbios para cornichão tolerantes à acidez e ao Al tóxico e eficientes na fixação biológica de N em solos de baixa fertilidade. Foram avaliados 52 isolados de rizóbios de Lotus spp. obtidos de solos de cinco localidades do Rio Grande do Sul. Os rizóbios foram avaliados quanto à diversidade genética, à tolerância a pH 4,2 e ao Al tóxico. Entre os rizóbios tolerantes a fatores de acidez, sete foram avaliados quanto à eficiência simbiótica com plantas, em casa de vegetação, em vasos com solo não estéril. Observou-se alta diversidade genética entre os rizóbios estudados, dos quais 16 foram tolerantes a pH 4,2 e a 50 µM de Al em meio de cultura, produzindo populações da ordem de 10(7) até 10(8) UFC mL-1. Os sete rizóbios testados em casa de vegetação superaram as estirpes atualmente recomendadas para a produção de inoculantes, o que demonstra a existência, em solos do Rio Grande do Sul, de rizóbios tolerantes à acidez do solo e eficientes como fixadores de N em plantas de cornichão. Birdsfoot trefoil is a perennial winter-spring forage legume, highly important in Rio Grande do Sul, in the south of Brazil. It stands out for the ability to survive in relatively acidic and nutrient-poor soils. This study aimed to select birdsfoot trefoil rhizobial strains with tolerance to acidity and aluminum toxicity and efficiency in nitrogen fixation in nutrient-poor soils. Fifty-two isolates of Lotus spp rhizobia from soils of five locations in the state of Rio Grande do Sul were evaluated. The strains were evaluated for genetic diversity and tolerance to pH 4.2 and to aluminum toxicity. Of the acid-tolerant rhizobia, seven were evaluated for symbiotic efficiency in plants grown in pots with non-sterile soil, in a greenhouse experiment. Genetic diversity in the studied rhizobia was high and 16 were tolerant to pH 4.2 and to 50 µM Al in media broth, reaching populations from 10(7) up to 10(8) CFU mL-1. The seven rhizobia tested in the greenhouse performed better than the strains recommended for inoculant production, demonstrating the existence of rhizobia tolerant to soil acidity and efficient in nitrogen fixation on birdsfoot trefoil plants in soils of Rio Grande do Sul.

A inoculação de plantas leguminosas com rizóbios é um dos principais métodos biotecnológicos de utilização de micro-organismos em plantas visando à fixação biológica de nitrogênio na agricultura. No entanto, nos últimos anos, vêm sendo observada nesses micro-organismos a capacidade de produção de fitohormônios, principalmente o ácido indol-acético (AIA) e a promoção de crescimento em gramíneas. Dessa forma, os objetivos deste trabalho foram quantificar o ácido indol-acético produzido por rizóbios isolados de alfafa, avaliar o efeito da inoculação desses micro-organismos na germinação de sementes de arroz e realizar a caracterização genética desses isolados. Nove rizóbios isolados de nódulos de alfafa foram avaliados quanto a sua capacidade de produção de equivalentes de AIA e a influência da inoculação desses micro-organismos na germinação e desenvolvimento de plântulas de arroz. Os rizóbios produtores de AIA foram identificados pelo sequenciamento da região do gene 16S do DNAr. A produção de equivalentes ao ácido indol-acético foi observada em todos rizóbios, com valores que variaram de 43,04 a 101,26µg mL-1 em meio de cultura. Com relação à germinação das sementes de arroz, a inoculação com rizóbios acelerou o processo e o crescimento de suas plântulas. Os rizóbios UFRGS Ms58, Ms515, Ms195, Ms205, Ms2010 e 2012 foram identificados como pertencentes à espécie Sinorhizobium meliloti e UFRGS Ms55, Ms72 e Ms75 à espécie Rhizobium sp. The inoculation of leguminous plants with rhizobia is one of the main methods of biotechnological use of microorganisms in order to obtain biological nitrogen fixation in agriculture. However, in recent years it has been attributed to these microorganisms the ability to produce phytohormones, mainly indole acetic acid (IAA), and to promote the growth in grasses. Thus, the objectives of this study were to quantify the indole acetic acid produced by rhizobia from alfalfa and to evaluate the effect of inoculation of these microorganisms on the germination of rice seed and to perform the genetic characterization of these isolates. Nine rhizobia, from nodules of alfalfa, were evaluated for their ability to produce IAA equivalents and for their influence in inoculating these microorganisms on germination and seedling development of rice. Moreover, these rhizobia producers of IAA were identified by the 16S region of DNAr. The equivalent production of indole acetic acid was observed in all tested isolates, with values ranging from 43.04 to 101.26µg mL-1 in culture medium. Regarding the germination of rice seeds, the inoculation with rhizobia accelerated this germination and its growth. Microorganisms UFRGS Ms58, UFRGS Ms515, UFRGS Ms195, UFRGS Ms205, UFRGS Ms2010 and UFRGS 2012 were identified as belonging to the species of Sinorhizobium meliloti. Microorganisms Ms55 UFRGS, UFRGS Ms75 and UFRG Ms72 were identified as belonging to the species of Rhizobium sp.