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Río Cuarto, Argentina

Costa F.M.,State University of Mato Grosso do Sul | Schiavo J.A.,State University of Mato Grosso do Sul | Brasil M.S.,Federal University of Mato Grosso do Sul | Leite J.,Federal Rural University of Rio de Janeiro | And 2 more authors.
Genetics and Molecular Research | Year: 2014

The aim of this study was to evaluate the diversity of rhizobial isolates obtained from root nodules of pigeonpea plants grown at the eastern edge of the Brazilian Pantanal. The bacterial isolates were isolated from root nodules from field-growing pigeonpea grown in two rural settlements of the Aquidauana municipality. The bacterial isolates were characterized phenotypically by means of cultural characterization, intrinsic antibiotic resistance (IAR), salt and high incubation temperature tolerance, and amylolytic and cellulolytic activities. The molecular characterization of the bacterial isolates was carried out using amplified ribosomal DNA restriction analysis (ARDRA) and Box-polymerase chain reaction (PCR) techniques. In addition, the symbiotic performance of selected rhizobial isolates was evaluated in a greenhouse experiment using sterile substrate. The phenotypic characterization revealed that the bacterial strains obtained from pigeonpea root nodules presented characteristics that are uncommon among rhizobial isolates, indicating the presence of new species nodulating the pigeonpea plants in the Brazilian Pantanal. The molecular fingerprinting of these bacterial isolates also showed a highly diverse collection, with both techniques revealing less than 25% similarity among bacterial isolates. The evaluation of symbiotic performance also indicated the presence of microorganisms with high potential to increase the growth and nitrogen content at the shoots of pigeonpea plants. The results obtained in this study indicate the presence of a highly diversified rhizobial community nodulating the pigeonpea at the eastern edge of the Brazilian Pantanal. © FUNPEC-RP.

Ferreira E.P.B.,Laboratorio Of Biologia Do Solo | Martins L.M.V.,UNEB | Xavier G.R.,Laboratorio Of Ecologia Microbiana | Rumjanek N.G.,Laboratorio Of Ecologia Microbiana
Revista Caatinga | Year: 2011

Aiming to evaluate the nodulation and grain yield by cowpea inoculated with rhizobia isolates obtained of soil samples from Brazilian Northeast region, an experiment was carried out in Leonard jars under greenhouse conditions. The experiment was performed on a randomized block design with five replicates and five sampling times, performed at 15, 30, 45, 60 and 75 days after emergence (DAE). Nine rhizobia isolates and the recommended strain (BR 2001) were inoculated on cowpea. Besides, it were used two control treatment: mineral nitrogen (TN, applying 150 mg N plant -1) and an absolute control (T0). Evaluating the number of nodules per plant (NN), nodule dry mass (NDM), plant dry matter (PDM), Accumulated N (N ac), grain dry mass (GDM) and straw dry mass of pods (DMP). Results showed that the NN, NDM, PDM and Nac content increased until 45 DAE. Although variations had been occurred after 60 DAE for these parameters, significant difference was only found for N ac content at 75 DAE. Evaluated parameters (NN, NDM, PDM and N ac) showed a high correlation with GDM. Although no statistical difference had been observed to the strain BR 2001, five of the nine Bradyrhizobia isolates provided GDM production from 1.6 to 2.4 times more than the recommended strain, indicating high potential of use of these isolates as inoculant. However, further experiments are needed, mostly under field conditions to confirm these results.

Ramos-Garza J.,National Polytechnic Institute of Mexico | Ramos-Garza J.,Laboratorio Of Ecologia Microbiana | Bustamante-Brito R.,National Polytechnic Institute of Mexico | Angeles de Paz G.,Laboratorio Of Nematologia Agricola | And 4 more authors.
Canadian Journal of Microbiology | Year: 2016

Yeasts were quantified and isolated from the rhizospheres of 5 plant species grown at 2 sites of a Mexican region contaminated with arsenic, lead, and other heavy metals. Yeast abundance was about 102 CFU/g of soil and 31 isolates were obtained. On the basis of the phylogenetic analysis of 26S rRNA and internal transcribed spacer fragment, 6 species were identified within the following 5 genera: Cryptococcus (80.64%), Rhodotorula (6.45%), Exophiala (6.45%), Trichosporon (3.22%), and Cystobasidium (3.22%). Cryptococcus spp. was the predominant group. Pectinases (51.6%), proteases (51.6%), and xylanases (41.9%) were the enzymes most common, while poor production of siderophores (16.1%) and indole acetic acid (9.67%) was detected. Isolates of Rhodotorula mucilaginosa and Cystobasidium sloffiae could promote plant growth and seed germination in a bioassay using Brassica juncea. Resistance of isolates by arsenic and heavy metals was as follows: As3+ ≥ 100 mmol/L, As5+ ≥ 30 mmol/L, Zn2+ ≥ 2 mmol/L, Pb2+ ≥ 1.2 mmol/L, and Cu2+ ≥ 0.5 mmol/L. Strains of Cryptococcus albidus were able to reduce arsenate (As5+) into arsenite (As3+), but no isolate was capable of oxidizing As3+. This is the first study on the abundance and identification of rhizosphere yeasts in a heavy-metal- and arsenic-contaminated soil, and of the reduction of arsenate by the species C. albidus. © 2016, Canadian Journal of Microbiology. All rights reserved.

Pereira P.,Laboratorio Of Ecologia Microbiana | Nesci A.,Laboratorio Of Ecologia Microbiana | Castillo C.,National University of Rio Cuarto | Etcheverry M.,Laboratorio Of Ecologia Microbiana
Biological Control | Year: 2010

The effects of four bacterial biocontrol agents on Fusarium verticillioides infection and fumonisin accumulation in the maize agroecosystem were evaluated in a 2-year field study. The antagonistic abilities of the four agents were examined following two application techniques consisting of inoculating seeds during pre-sowing and maize ears at flowering. Seed inoculation with F. verticillioides and co-inoculation with this fungus and each of the four agents were also examined. Treatment effects on maize performance were also assessed through determination of the number of plants per hectare, kernels yield (kg ha-1) and kernel-cob relations. F. verticillioides infection and fumonisin B1 contents were determined in kernels of physiologically mature maize plants at harvest time. Maize yield remained unchanged with respect to controls in both field surveys; however significantly higher FB1 contents were obtained after inoculation of seeds with F. verticillioides M7075. Seed treatment with Bacillus amyloliquefaciens and Enterobacter hormaechei reduced the infection by the fungus and FB1 contents both years of the study while ear inoculation produced highly variable results. The number of colony forming units of F. verticillioides obtained from harvested maize kernels was positively correlated with fumonisin B1 content; however none of these parameters showed significant correlation with kernel yield. The overall results suggest that in years conducive for F. verticillioides infection and fumonisin production, seed treatment with Bacillus amyloliquefaciens and Enterobacter hormaechei may improve quality of maize grains obtained at harvest by reducing toxin content. © 2010 Elsevier Inc. All rights reserved.

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