Previous studies estimated that sugarcane could obtain up to 60% of total nitrogen accumulated fr... more Previous studies estimated that sugarcane could obtain up to 60% of total nitrogen accumulated from BNF. Here a mixture of five endophytic diazotrophic strains was tested in a field trial, inoculated in two micropropagated sugarcane varieties and three locals, to determine the effects on commercial crop conditions. The sugarcane plantlets were inoculated in vitro, and after 17 months of growing in the field, the productivity and BNF contribution showed to be influenced by the plant genotype and soil type. The highest BNF contributions was observed in the poorest soil for both varieties. Smaller increases in productivity were observed for SP 701143 variety grown in soil with low or medium fertility. In contrast, a decrease in the stem productivity was observed in the SP 813250 variety grown in the three localities.
SummaryBradyrhizobium spp. are well known to mediate biological nitrogen fixation (BNF) as micros... more SummaryBradyrhizobium spp. are well known to mediate biological nitrogen fixation (BNF) as microsymbionts inhabiting nodules on leguminous plants. However, they may also contribute to plant growth via free‐living N2 fixation (FLNF) in association with non‐legumes. Notably, several Bradyrhizobium strains from sugarcane roots display FLNF activity. Among them, Bradyrhizobium sacchari is a legume symbiotic species, whereas strains AG48 and M12 are non‐symbiotic. In the present study, a phylogenomic approach was applied to study peculiarities of these and other Bradyrhizobium strains with respect to N fixation (nif) gene content in order to reveal genetic features that enable FNLF in Bradyrhizobium spp. All FLNF strains carry an ancestral ‘non‐symbiotic’ nif‐gene cluster (NSC). B. sacchari also contains a second ‘symbiotic’ nif‐gene cluster (SC), a characteristic observed in only three of 156 evaluated genomes. B. sacchari stood out and presented a high level of sequence divergence between individual nif‐gene homologues and we discuss scenarios for the evolutionary origin of these clusters. The transcript level of NSC nifH gene increased during FLNF, when compared to symbiotic conditions. The data suggest that sugarcane roots harbor diverse Bradyrhizobium spp. that are genetically adapted to a dynamic environment where leguminous and non‐leguminous host plants are alternately available.
Aims Rhizobia are common members of plant microbiomes. This study aimed to evaluate if rhizobia c... more Aims Rhizobia are common members of plant microbiomes. This study aimed to evaluate if rhizobia can colonize sugarcane mini-setts and if and how they affect sprouting and morphological traits of plant development. Methods Bradyrhizobium sacchari strain BR 10280 T and Rhizobium sp. strain BR 10268 were inoculated on sugarcane mini-setts and sprouting and plant development were evaluated. Bacterial production of hormones and their effect on plant growth were studied using HPLC and GC-MS / SIM and sugarcane sprouting assays. Colonization was investigated by colony counting and CLSM. Sequence analysis of recA, gyrB and rpoB genes was applied to refine the phylogenetic classification of strain BR 10268. Results BR 10268 had a positive effect on sugarcane mini-sett sprouting and shoot and root growth at 30 and 75 days after transplantation (DAT) and colonized sprouting mini-sett tissues. Few significant effects were observed for B. sacchari BR 10280 T. Cell-free BR 10268 supernatant was found to contain gibberellins (GAs) and low concentrations of indole-3-acetic acid (IAA) and trans-zeatin; treatment of mini-setts with GA 3 (0.15 or 1.5 μg mL −1) affected sprouting in a similar manner as BR 10268 inoculation. BR 10268 was found to be phylogenetically close to R. freirei. Conclusions Rhizobium sp. BR 10268 positively affects sprouting and growth of sugarcane, probably via production of plant hormonal substances, notably gibberellins, thus naturally occurring rhizobia may have potential as sugarcane inoculants.
The inoculation technique with endophytic diazotrophic bacteria in sugarcane has been shown as an... more The inoculation technique with endophytic diazotrophic bacteria in sugarcane has been shown as an alternative practice to plant growth promotion. The aim of this work was to evaluate the biological nitrogen fixation (BNF) contribution by different strains of Herbaspirillum seropedicae and Gluconacetobacter diazotrophicus in sugarcane plant inoculated from seeds. The seeds were planted in pots filled with nonsterile soil, inoculated with the bacterial strains and grown 10 months outside of the greenhouse. The BNF contribution of the inoculated bacteria varied depending on the plant species used as a control. The highest BNF contribution as well as the highest populations of reisolated bacteria was observed with inoculation of H. seropedicae strains. The roots appeared to be the preferential tissues for the establishment of the inoculated species.
Resumo-O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diaz... more Resumo-O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diazotrophicus oriunda de cultivares de cana-de-açúcar (Saccharum spp.) de diferentes regiões e bancos de germoplasma. O estudo foi realizado com 123 isolados, obtidos de folhas, colmos e raízes de 80 espécies e híbridos de cana-deaçúcar, procedentes de diferentes países e mantidos em coleções de germoplasma nos Estados da Bahia e Rio de Janeiro. Foram utilizados cinco isolados obtidos de plantas de café (Coffea arabica), dois de abacaxi (Ananas comosus) e um de Pennisetum purpureum e mais 10 estirpes com padrões eletroforéticos distintos, após o uso de enzimas comuns do metabolismo microbiano (MLEE). O agrupamento obtido por meio da técnica de imunoadsorção com enzima acoplada (ELISA) sugere que as variações expressas pelos isolados não estão relacionadas com a espécie de planta, a variedade de cana-de-açúcar, a origem geográfica, a parte da planta de onde os isolados foram obtidos e o tempo de amostragem. Altas doses de nitrogênio levaram à diminuição da diversidade de G. diazotrophicus. Termos para indexação: ELISA, fixação biológica de nitrogênio, bactérias endofíticas. Diversity of Gluconacetobacter diazotrophicus isolated from sugarcane plants cultivated in Brazil Abstract-The objective of this study was to evaluate the diversity of Gluconacetobacter diazotrophicus isolates from different sugarcane (Saccharum spp.) varieties. This study was developed using 123 strains from the internal tissues of stems and roots, isolated from 80 species and hybrids of sugarcane, originated from different countries and maintained in two germoplasm collections localized in Bahia and Rio de Janeiro States. Five isolates obtained from coffee plants (Coffea arabica), two from pineapple (Ananas comosus), one from Pennisetum purpureum and 10 strains, which present different electrophoretic patterns, were used in the comparison. Cluster analysis of enzyme-linked immunosorbent assay (ELISA) results suggested that variations were not correlated with the plant species, sugarcane variety, geographic origin, parts of plants nor with sampling time. High nitrogen doses lowered the diversity of G. diazotrophicus.
Current plant science and biotechnology in agriculture, 1998
Very little is known about the role of the plant in the association between sugarcane and the end... more Very little is known about the role of the plant in the association between sugarcane and the endophytic diazotrophs A. diazotrophicus and Herbaspirillum spp. The differences of the contribution of BNF in distinct sugarcane genotypes indicate that plant genetic factors are contributing to the efficiency of the process. The susceptibility of some cultivars to H. rubrisubalbicans strengthen the hypothesis that the mechanism of plant/bacteria interaction in this association is dependent on the plant genetic information. In order to elucidate the role of the plant in this interaction, plant genes induced by the association with the bacteria are being isolated by the technique of ddRT-PCR. Plants microorganism-free, obtained by in vitro meristem culture, are being inoculated only with A. diazotrophicus, only with Herbaspirillum spp., with a Herbaspirillum mutant that does not fix nitrogen and with a mixture of A. diazotrophicus and Herbaspirillum spp. Among the differentially expressed fragments isolated, two are being further characterized. One of the genes, called MisA2, is expressed only in plants infected with the mixture of bacteria. The deduced amino acid sequence of a partial cDNA isolated does not show significant homology with any described protein of the DataBank. Nevertheless, it has some features which could indicate a possible function. The protein is proline-rich, a feature of some nodulins which are suggested to be located in the cell wall formed inside the infection thread. The other gene, called AcA5, is induced in plants infected either with A. diazotrophicus or Herbaspirillum spp., or with the mixture of bacteria, but not with the mutant. The sugarcane gene is homologous to an endossomal membrane protein of yeast. The function of the isolated genes in the interaction are still unknown.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
While numerous isolations of diazotrophic bacteria from sugarcane in different countries and regi... more While numerous isolations of diazotrophic bacteria from sugarcane in different countries and regions have led to the characterization of many new species of diazotrophic bacteria in the last decades, the question still remains whether these bacteria represent the complete community of diazotrophic bacteria in sugarcane plants, which actively fix nitrogen in planta (rhizosphere, roots, stems and leaves). Therefore, cultivation-independent molecular approaches to characterize the diazotrophic bacterial community of sugarcane, which may provide information about hitherto not cultivated bacteria contributing biologically fixed nitrogen to sugarcane plants were carried out. The experiments were conducted from 2008 to 2009 at Embrapa-Agrobiologia in Seropédica, Rio de Janeiro, Brazil, with the sugarcane cultivar RB867515, which is currently one of the most used sugarcane cultivars in Brazil. In these greenhouse and field studies, polymerase chain reaction (PCR) amplification of 16S rDNA and nifH DNA as well as 16S-cDNA and nifH-cDNA was performed using DNA and RNA extracted from roots and leave sheaths of sugarcane. A number of sequences were retrieved from genera and species that had been already characterized by the cultivation approach, although it appeared that the diversity reflected by the amplified sequences was much higher in terms of different bacterial species (which may not have been characterized in detail yet). However, many bacterial sequences that were not represented in the existing cultured strains, such as Ideonella, Bradyrhizobium or Rhizobium, also appeared. Interestingly, some of these species represented apparently active nitrogen-fixing bacteria in the sugarcane tissues, because we frequently found them within the RNA-pool (16S-cDNA- and nifH-cDNA-sequence libraries). Therefore, attempts were made to cultivate Bradyrhizobium bacteria from the same field-grown sugarcane variety, using new isolation approaches that have not yet been applied to sugarcane, such as enrichment with promiscuous leguminous trap plants, for example, Vigna unguiculata (cowpea). Indeed, a high diversity of Bradyrhizobium spp. could be isolated, which were found to fix nitrogen – at least to some extent – also in vitro. These newly isolated nitrogen-fixing bacteria resembled part of the sequences retrieved from the same plant material using cultivation-independent approaches. It remains to be investigated whether these bacteria are indeed able to contribute substantial amounts of fixed nitrogen to sugarcane, which has been repeatedly demonstrated using 15N-natural abundance and dilution techniques
The objective of this work was to evaluate the diversity of endophytic diazotrophic bacteria of t... more The objective of this work was to evaluate the diversity of endophytic diazotrophic bacteria of the genera Herbaspirillum and Burkholderia, in two rice varieties, considered of high (IR 42) and low (IAC 4440) contribution on BNF. Two experiments were conducted in greenhouse conditions, in order to study the association of endophytic diazotrophic bacteria with wetland rice varieties, which were planted in two types of soil: one from Rio de Janeiro State and another from Goias State, Brazil. Bacteria] population (in different parts) and physiological stages of the plants were evaluated, followed by the both genera strains isolation using culture media. The isolated bacteria were characterized based on morphological and physiological aspects. High bacterial counts were detected (10(6) cells g(-1) fresh weight), especially in root samples of both rice varieties. The majority of the isolates were used for characterization, and the data obtained from the similarity matrix showed the prese...
Nitrogen Fixation: From Molecules to Crop Productivity, 2000
Investigating the diversity of diazotrophic bacteria associated with plant roots of less well stu... more Investigating the diversity of diazotrophic bacteria associated with plant roots of less well studied plants, isolates of well known and new species could be found. The diversity on the strain level was rather restricted for endophytic bacteria in a given plant, which argues for a specificity of colonization. The mechanism of this specificity is not understood.
O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diazotrophi... more O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diazotrophicus oriunda de cultivares de cana-de-açúcar (Saccharum spp.) de diferentes regiões e bancos de germoplasma. O estudo foi realizado com 123 isolados, obtidos de folhas, colmos e raízes de 80 espécies e híbridos de cana-de-açúcar, procedentes de diferentes países e mantidos em coleções de germoplasma nos Estados da Bahia e Rio de Janeiro. Foram utilizados cinco isolados obtidos de plantas de café (Coffea arabica), dois de abacaxi (Ananas comosus) e um de Pennisetum purpureum e mais 10 estirpes com padrões eletroforéticos distintos, após o uso de enzimas comuns do metabolismo microbiano (MLEE). O agrupamento obtido por meio da técnica de imunoadsorção com enzima acoplada (ELISA) sugere que as variações expressas pelos isolados não estão relacionadas com a espécie de planta, a variedade de cana-de-açúcar, a origem geográfica, a parte da planta de onde os isolados foram obtidos e o tempo de a...
O objetivo deste trabalho foi avaliar a diversidade de bactérias diazotróficas endofíticas, dos g... more O objetivo deste trabalho foi avaliar a diversidade de bactérias diazotróficas endofíticas, dos gêneros Herbaspirillum e Burkholderia, em duas variedades de arroz, consideradas de alta (IR 42) e baixa (IAC 4440) eficiência de fixação biológica de nitrogênio. Foram realizados dois experimentos em casa de vegetação, em vasos com dois tipos de solos, provenientes dos Estados de Goiás e do Rio de Janeiro. Foi feita a contagem do número de bactérias e o isolamento em diferentes partes e estágios de desenvolvimento das plantas, mediante o uso de meios de cultivo JNFb e JMV. Os isolados bacterianos foram caracterizados a partir de aspectos morfológicos das colônias, com o crescimento em meios de cultivo, e de testes fisiológicos (uso de fontes de carbono e atividade de redução de acetileno). A contagem revelou grande número de bactérias diazotróficas (10(6) células g-1 matéria fresca), presentes em ambas as variedades de arroz, principalmente nas amostras radiculares. Os dados, obtidos na ...
Micropropagated plantlets of sugar cane were inoculated with the N2-fixing bacterium Acetobacter ... more Micropropagated plantlets of sugar cane were inoculated with the N2-fixing bacterium Acetobacter diazotrophicus. Various modifications on the basic plant culture medium MS were made for the plant/bacteria association. The protocol required the inoculation of the bacteria at the end of the rooting period in a medium without hormones or vitamins, and with the concentration of sugar and mineral nutrients reduced
The aim of this work was to evaluate the effect of the inoculation of endophytic N2-fixing bacter... more The aim of this work was to evaluate the effect of the inoculation of endophytic N2-fixing bacteria on the development of micropropagated sugarcane plants. The endophytic population of each inoculated species was monitored during the growth period, and biological nitrogen fixation (BNF) contribution of each inoculation treatment was assessed using the 15N-isotope dilution technique. Seven different combinations of inoculum were
Reis (2017) Yield of sugarcane varieties and their sugar quality grown in different soil types an... more Reis (2017) Yield of sugarcane varieties and their sugar quality grown in different soil types and inoculated with a diazotrophic bacteria consortium,
Previous studies estimated that sugarcane could obtain up to 60% of total nitrogen accumulated fr... more Previous studies estimated that sugarcane could obtain up to 60% of total nitrogen accumulated from BNF. Here a mixture of five endophytic diazotrophic strains was tested in a field trial, inoculated in two micropropagated sugarcane varieties and three locals, to determine the effects on commercial crop conditions. The sugarcane plantlets were inoculated in vitro, and after 17 months of growing in the field, the productivity and BNF contribution showed to be influenced by the plant genotype and soil type. The highest BNF contributions was observed in the poorest soil for both varieties. Smaller increases in productivity were observed for SP 701143 variety grown in soil with low or medium fertility. In contrast, a decrease in the stem productivity was observed in the SP 813250 variety grown in the three localities.
SummaryBradyrhizobium spp. are well known to mediate biological nitrogen fixation (BNF) as micros... more SummaryBradyrhizobium spp. are well known to mediate biological nitrogen fixation (BNF) as microsymbionts inhabiting nodules on leguminous plants. However, they may also contribute to plant growth via free‐living N2 fixation (FLNF) in association with non‐legumes. Notably, several Bradyrhizobium strains from sugarcane roots display FLNF activity. Among them, Bradyrhizobium sacchari is a legume symbiotic species, whereas strains AG48 and M12 are non‐symbiotic. In the present study, a phylogenomic approach was applied to study peculiarities of these and other Bradyrhizobium strains with respect to N fixation (nif) gene content in order to reveal genetic features that enable FNLF in Bradyrhizobium spp. All FLNF strains carry an ancestral ‘non‐symbiotic’ nif‐gene cluster (NSC). B. sacchari also contains a second ‘symbiotic’ nif‐gene cluster (SC), a characteristic observed in only three of 156 evaluated genomes. B. sacchari stood out and presented a high level of sequence divergence between individual nif‐gene homologues and we discuss scenarios for the evolutionary origin of these clusters. The transcript level of NSC nifH gene increased during FLNF, when compared to symbiotic conditions. The data suggest that sugarcane roots harbor diverse Bradyrhizobium spp. that are genetically adapted to a dynamic environment where leguminous and non‐leguminous host plants are alternately available.
Aims Rhizobia are common members of plant microbiomes. This study aimed to evaluate if rhizobia c... more Aims Rhizobia are common members of plant microbiomes. This study aimed to evaluate if rhizobia can colonize sugarcane mini-setts and if and how they affect sprouting and morphological traits of plant development. Methods Bradyrhizobium sacchari strain BR 10280 T and Rhizobium sp. strain BR 10268 were inoculated on sugarcane mini-setts and sprouting and plant development were evaluated. Bacterial production of hormones and their effect on plant growth were studied using HPLC and GC-MS / SIM and sugarcane sprouting assays. Colonization was investigated by colony counting and CLSM. Sequence analysis of recA, gyrB and rpoB genes was applied to refine the phylogenetic classification of strain BR 10268. Results BR 10268 had a positive effect on sugarcane mini-sett sprouting and shoot and root growth at 30 and 75 days after transplantation (DAT) and colonized sprouting mini-sett tissues. Few significant effects were observed for B. sacchari BR 10280 T. Cell-free BR 10268 supernatant was found to contain gibberellins (GAs) and low concentrations of indole-3-acetic acid (IAA) and trans-zeatin; treatment of mini-setts with GA 3 (0.15 or 1.5 μg mL −1) affected sprouting in a similar manner as BR 10268 inoculation. BR 10268 was found to be phylogenetically close to R. freirei. Conclusions Rhizobium sp. BR 10268 positively affects sprouting and growth of sugarcane, probably via production of plant hormonal substances, notably gibberellins, thus naturally occurring rhizobia may have potential as sugarcane inoculants.
The inoculation technique with endophytic diazotrophic bacteria in sugarcane has been shown as an... more The inoculation technique with endophytic diazotrophic bacteria in sugarcane has been shown as an alternative practice to plant growth promotion. The aim of this work was to evaluate the biological nitrogen fixation (BNF) contribution by different strains of Herbaspirillum seropedicae and Gluconacetobacter diazotrophicus in sugarcane plant inoculated from seeds. The seeds were planted in pots filled with nonsterile soil, inoculated with the bacterial strains and grown 10 months outside of the greenhouse. The BNF contribution of the inoculated bacteria varied depending on the plant species used as a control. The highest BNF contribution as well as the highest populations of reisolated bacteria was observed with inoculation of H. seropedicae strains. The roots appeared to be the preferential tissues for the establishment of the inoculated species.
Resumo-O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diaz... more Resumo-O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diazotrophicus oriunda de cultivares de cana-de-açúcar (Saccharum spp.) de diferentes regiões e bancos de germoplasma. O estudo foi realizado com 123 isolados, obtidos de folhas, colmos e raízes de 80 espécies e híbridos de cana-deaçúcar, procedentes de diferentes países e mantidos em coleções de germoplasma nos Estados da Bahia e Rio de Janeiro. Foram utilizados cinco isolados obtidos de plantas de café (Coffea arabica), dois de abacaxi (Ananas comosus) e um de Pennisetum purpureum e mais 10 estirpes com padrões eletroforéticos distintos, após o uso de enzimas comuns do metabolismo microbiano (MLEE). O agrupamento obtido por meio da técnica de imunoadsorção com enzima acoplada (ELISA) sugere que as variações expressas pelos isolados não estão relacionadas com a espécie de planta, a variedade de cana-de-açúcar, a origem geográfica, a parte da planta de onde os isolados foram obtidos e o tempo de amostragem. Altas doses de nitrogênio levaram à diminuição da diversidade de G. diazotrophicus. Termos para indexação: ELISA, fixação biológica de nitrogênio, bactérias endofíticas. Diversity of Gluconacetobacter diazotrophicus isolated from sugarcane plants cultivated in Brazil Abstract-The objective of this study was to evaluate the diversity of Gluconacetobacter diazotrophicus isolates from different sugarcane (Saccharum spp.) varieties. This study was developed using 123 strains from the internal tissues of stems and roots, isolated from 80 species and hybrids of sugarcane, originated from different countries and maintained in two germoplasm collections localized in Bahia and Rio de Janeiro States. Five isolates obtained from coffee plants (Coffea arabica), two from pineapple (Ananas comosus), one from Pennisetum purpureum and 10 strains, which present different electrophoretic patterns, were used in the comparison. Cluster analysis of enzyme-linked immunosorbent assay (ELISA) results suggested that variations were not correlated with the plant species, sugarcane variety, geographic origin, parts of plants nor with sampling time. High nitrogen doses lowered the diversity of G. diazotrophicus.
Current plant science and biotechnology in agriculture, 1998
Very little is known about the role of the plant in the association between sugarcane and the end... more Very little is known about the role of the plant in the association between sugarcane and the endophytic diazotrophs A. diazotrophicus and Herbaspirillum spp. The differences of the contribution of BNF in distinct sugarcane genotypes indicate that plant genetic factors are contributing to the efficiency of the process. The susceptibility of some cultivars to H. rubrisubalbicans strengthen the hypothesis that the mechanism of plant/bacteria interaction in this association is dependent on the plant genetic information. In order to elucidate the role of the plant in this interaction, plant genes induced by the association with the bacteria are being isolated by the technique of ddRT-PCR. Plants microorganism-free, obtained by in vitro meristem culture, are being inoculated only with A. diazotrophicus, only with Herbaspirillum spp., with a Herbaspirillum mutant that does not fix nitrogen and with a mixture of A. diazotrophicus and Herbaspirillum spp. Among the differentially expressed fragments isolated, two are being further characterized. One of the genes, called MisA2, is expressed only in plants infected with the mixture of bacteria. The deduced amino acid sequence of a partial cDNA isolated does not show significant homology with any described protein of the DataBank. Nevertheless, it has some features which could indicate a possible function. The protein is proline-rich, a feature of some nodulins which are suggested to be located in the cell wall formed inside the infection thread. The other gene, called AcA5, is induced in plants infected either with A. diazotrophicus or Herbaspirillum spp., or with the mixture of bacteria, but not with the mutant. The sugarcane gene is homologous to an endossomal membrane protein of yeast. The function of the isolated genes in the interaction are still unknown.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
While numerous isolations of diazotrophic bacteria from sugarcane in different countries and regi... more While numerous isolations of diazotrophic bacteria from sugarcane in different countries and regions have led to the characterization of many new species of diazotrophic bacteria in the last decades, the question still remains whether these bacteria represent the complete community of diazotrophic bacteria in sugarcane plants, which actively fix nitrogen in planta (rhizosphere, roots, stems and leaves). Therefore, cultivation-independent molecular approaches to characterize the diazotrophic bacterial community of sugarcane, which may provide information about hitherto not cultivated bacteria contributing biologically fixed nitrogen to sugarcane plants were carried out. The experiments were conducted from 2008 to 2009 at Embrapa-Agrobiologia in Seropédica, Rio de Janeiro, Brazil, with the sugarcane cultivar RB867515, which is currently one of the most used sugarcane cultivars in Brazil. In these greenhouse and field studies, polymerase chain reaction (PCR) amplification of 16S rDNA and nifH DNA as well as 16S-cDNA and nifH-cDNA was performed using DNA and RNA extracted from roots and leave sheaths of sugarcane. A number of sequences were retrieved from genera and species that had been already characterized by the cultivation approach, although it appeared that the diversity reflected by the amplified sequences was much higher in terms of different bacterial species (which may not have been characterized in detail yet). However, many bacterial sequences that were not represented in the existing cultured strains, such as Ideonella, Bradyrhizobium or Rhizobium, also appeared. Interestingly, some of these species represented apparently active nitrogen-fixing bacteria in the sugarcane tissues, because we frequently found them within the RNA-pool (16S-cDNA- and nifH-cDNA-sequence libraries). Therefore, attempts were made to cultivate Bradyrhizobium bacteria from the same field-grown sugarcane variety, using new isolation approaches that have not yet been applied to sugarcane, such as enrichment with promiscuous leguminous trap plants, for example, Vigna unguiculata (cowpea). Indeed, a high diversity of Bradyrhizobium spp. could be isolated, which were found to fix nitrogen – at least to some extent – also in vitro. These newly isolated nitrogen-fixing bacteria resembled part of the sequences retrieved from the same plant material using cultivation-independent approaches. It remains to be investigated whether these bacteria are indeed able to contribute substantial amounts of fixed nitrogen to sugarcane, which has been repeatedly demonstrated using 15N-natural abundance and dilution techniques
The objective of this work was to evaluate the diversity of endophytic diazotrophic bacteria of t... more The objective of this work was to evaluate the diversity of endophytic diazotrophic bacteria of the genera Herbaspirillum and Burkholderia, in two rice varieties, considered of high (IR 42) and low (IAC 4440) contribution on BNF. Two experiments were conducted in greenhouse conditions, in order to study the association of endophytic diazotrophic bacteria with wetland rice varieties, which were planted in two types of soil: one from Rio de Janeiro State and another from Goias State, Brazil. Bacteria] population (in different parts) and physiological stages of the plants were evaluated, followed by the both genera strains isolation using culture media. The isolated bacteria were characterized based on morphological and physiological aspects. High bacterial counts were detected (10(6) cells g(-1) fresh weight), especially in root samples of both rice varieties. The majority of the isolates were used for characterization, and the data obtained from the similarity matrix showed the prese...
Nitrogen Fixation: From Molecules to Crop Productivity, 2000
Investigating the diversity of diazotrophic bacteria associated with plant roots of less well stu... more Investigating the diversity of diazotrophic bacteria associated with plant roots of less well studied plants, isolates of well known and new species could be found. The diversity on the strain level was rather restricted for endophytic bacteria in a given plant, which argues for a specificity of colonization. The mechanism of this specificity is not understood.
O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diazotrophi... more O objetivo deste trabalho foi avaliar a diversidade da população de Gluconacetobacter diazotrophicus oriunda de cultivares de cana-de-açúcar (Saccharum spp.) de diferentes regiões e bancos de germoplasma. O estudo foi realizado com 123 isolados, obtidos de folhas, colmos e raízes de 80 espécies e híbridos de cana-de-açúcar, procedentes de diferentes países e mantidos em coleções de germoplasma nos Estados da Bahia e Rio de Janeiro. Foram utilizados cinco isolados obtidos de plantas de café (Coffea arabica), dois de abacaxi (Ananas comosus) e um de Pennisetum purpureum e mais 10 estirpes com padrões eletroforéticos distintos, após o uso de enzimas comuns do metabolismo microbiano (MLEE). O agrupamento obtido por meio da técnica de imunoadsorção com enzima acoplada (ELISA) sugere que as variações expressas pelos isolados não estão relacionadas com a espécie de planta, a variedade de cana-de-açúcar, a origem geográfica, a parte da planta de onde os isolados foram obtidos e o tempo de a...
O objetivo deste trabalho foi avaliar a diversidade de bactérias diazotróficas endofíticas, dos g... more O objetivo deste trabalho foi avaliar a diversidade de bactérias diazotróficas endofíticas, dos gêneros Herbaspirillum e Burkholderia, em duas variedades de arroz, consideradas de alta (IR 42) e baixa (IAC 4440) eficiência de fixação biológica de nitrogênio. Foram realizados dois experimentos em casa de vegetação, em vasos com dois tipos de solos, provenientes dos Estados de Goiás e do Rio de Janeiro. Foi feita a contagem do número de bactérias e o isolamento em diferentes partes e estágios de desenvolvimento das plantas, mediante o uso de meios de cultivo JNFb e JMV. Os isolados bacterianos foram caracterizados a partir de aspectos morfológicos das colônias, com o crescimento em meios de cultivo, e de testes fisiológicos (uso de fontes de carbono e atividade de redução de acetileno). A contagem revelou grande número de bactérias diazotróficas (10(6) células g-1 matéria fresca), presentes em ambas as variedades de arroz, principalmente nas amostras radiculares. Os dados, obtidos na ...
Micropropagated plantlets of sugar cane were inoculated with the N2-fixing bacterium Acetobacter ... more Micropropagated plantlets of sugar cane were inoculated with the N2-fixing bacterium Acetobacter diazotrophicus. Various modifications on the basic plant culture medium MS were made for the plant/bacteria association. The protocol required the inoculation of the bacteria at the end of the rooting period in a medium without hormones or vitamins, and with the concentration of sugar and mineral nutrients reduced
The aim of this work was to evaluate the effect of the inoculation of endophytic N2-fixing bacter... more The aim of this work was to evaluate the effect of the inoculation of endophytic N2-fixing bacteria on the development of micropropagated sugarcane plants. The endophytic population of each inoculated species was monitored during the growth period, and biological nitrogen fixation (BNF) contribution of each inoculation treatment was assessed using the 15N-isotope dilution technique. Seven different combinations of inoculum were
Reis (2017) Yield of sugarcane varieties and their sugar quality grown in different soil types an... more Reis (2017) Yield of sugarcane varieties and their sugar quality grown in different soil types and inoculated with a diazotrophic bacteria consortium,
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