Journal articles: 'Rhizosphere competence'

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Ahmad, Jaleed S. "Rhizosphere Competence ofTrichoderma harzianum." Phytopathology 77, no. 2 (1987): 182. http://dx.doi.org/10.1094/phyto-77-182.

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Al-Rawahi, A. K., and J. G. Hancock. "Rhizosphere Competence of Pythium oligandrum." Phytopathology® 87, no. 9 (September 1997): 951–59. http://dx.doi.org/10.1094/phyto.1997.87.9.951.

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The associations of Pythium oligandrum with the root cortex, rhizoplane, and rhizosphere were measured with 11 crop species. This work was expedited by the use of a semiselective technique for isolation of P. oligandrum from soil and plant material. Cortical colonization of roots by P. oligandrum was not detected, and the rhizoplanes of the roots of most crops were free of the fungus. However, P. oligandrum was detected in large quantities with every crop tested when roots with adhering soil (rhizosphere soil) were assayed. Different crop species and cultivars of cantaloupe, cauliflower, and tomato varied in rhizosphere densities of P. oligandrum, but rhizosphere population densities of the fungus were consistently higher than in nonrhizosphere soils with plants grown in P. oligandrum-infested sterilized potting mix or an unsterilized mineral soil. After transplanting tomatoes into potting mix infested with P. oligandrum, increases in CFU occurred over time in the rhizosphere but not in the nonrhizosphere soil. In trials on delivery methods of inoculum of P. oligandrum, the rhizosphere populations of tomato plants grown in potting mix were about sixfold higher compared to seed-coat treatments when ground, alginate pelleted oospores were applied to seedlings growing in plug containers prior to transplanting or to pots containing potting mix before direct seeding.

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Ahmad, Jaleed S., and Ralph Baker. "Implications of rhizosphere competence of Trichoderma harzianum." Canadian Journal of Microbiology 34, no. 3 (March 1, 1988): 229–34. http://dx.doi.org/10.1139/m88-043.

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Seed treatment with conidia of rhizosphere-competent mutants of Trichoderma harzianum reduced the incidence of preemergence damping-off of barley, cucumber, pea, radish, and tomato induced by Pythium ultimum. Wild-type parents of these mutants were less effective in control. When rhizosphere-competent mutants were applied to seed or when a peat-bran preparation was added to soil, the resulting plants produced significantly higher fruit weight and higher dry weights than those treated with rhizosphere-incompetent wild types and controls. Seed treatment with mutants increased the incidence of emergence and resultant plant growth was significantly (P = 0.05) better than when mutant strains were added to soil in peat–bran. There was, however, no significant (P = 0.05) difference between the two types of application of the wild types. When cucumber seeds, treated with a T. harzianum rhizosphere-competent mutant (T-95) or its parent wild type (WT), were sown in raw soil kept under constant matric potential with no additional water added, the roots grew 8 cm in 8 days. Untreated seeds produced roots 7 cm long. Fewer colony-forming units of P. ultimum per milligram were isolated from rhizosphere soil of the T-95 treated seedlings than in the untreated controls and those treated with WT. Pythium ultimum was not detected in the 8th cm (farthest from seed) root segment of T-95 treated seeds, whereas the last centimetre of root segment from untreated and WT-treated seeds yielded 3000 colony-forming units/g rhizosphere soil. Seed treatment with rhizosphere-competent mutants of T. harzianum is an effective delivery system to achieve biocontrol and increase growth response.

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Ocamb, Cynthia M. "Rhizosphere Competence ofFusariumSpecies Colonizing Corn Roots." Phytopathology 84, no. 2 (1994): 166. http://dx.doi.org/10.1094/phyto-84-166.

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Hozore, Elissa, and Martin Alexander. "Bacterial characteristics important to rhizosphere competence." Soil Biology and Biochemistry 23, no. 8 (January 1991): 717–23. http://dx.doi.org/10.1016/0038-0717(91)90140-f.

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Ahmad, Jaleed S., and Ralph Baker. "Rhizosphere competence of benomyl-tolerant mutants of Trichoderma spp." Canadian Journal of Microbiology 34, no. 5 (May 1, 1988): 694–96. http://dx.doi.org/10.1139/m88-116.

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Two strains of Trichoderma harzianum and one each of T. koningii, T. polysporum, and T. viride were mutated for tolerance to the fungicide benomyl. Rhizosphere competence index of several mutants of each strain and species was determined by the rhizosphere competence assay. Most of the mutants and not their wild type parents were rhizosphere competent. When the strains and species were grown in Czapek–Dox broth for 6 days with cellulose as sole carbon source, the mutants produced significantly higher dry weight than their parent wild types. Neither the mutants nor the wild types produced biomass in glucose comparable to that in cellulose. Evidence indicates that Trichoderma spp. were induced by mutation to increase their linear growth rate and to become rhizosphere competent. Tolerance to benomyl does not seem to be a necessary attribute of rhizosphere competence.

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Raaijmakers, Jos M., Lentse van der Sluis, Peter A. H. M. Bakker, Bob Schippers, Margot Koster, and Peter J. Weisbeek. "Utilization of heterologous siderophores and rhizosphere competence of fluorescent Pseudomonas spp." Canadian Journal of Microbiology 41, no. 2 (February 1, 1995): 126–35. http://dx.doi.org/10.1139/m95-017.

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In this study, the potential of different Pseudomonas strains to utilize heterologous siderophores was compared with their competitiveness in the rhizosphere of radish. This issue was investigated in interactions between Pseudomonas putida WCS358 and Pseudomonas fluoresceins WCS374 and in interactions between strain WCS358 and eight indigenous Pseudomonas strains capable of utilizing pseudobactin 358. During four successive plant growth cycles of radish, strain WCS358 significantly reduced rhizosphere population densities of the wild-type strain WCS374 by up to 30 times, whereas derivative strain WCS374(pMR), harboring the siderophore receptor PupA for ferric pseudobactin 358, maintained its population density. Studies involving interactions between strain WCS358 and eight different indigenous Pseudomonas strains demonstrated that despite the ability of these indigenous isolates to utilize pseudobactin 358, their rhizosphere population densities were significantly reduced by strain WCS358 by up to 20 times. Moreover, rhizosphere colonization by WCS358 was not affected by any of these indigenous strains, even though siderophore-mediated growth inhibition of WCS358 by a majority of these strains was demonstrated in a plate bioassay. In conclusion, it can be stated that siderophore-mediated competition for iron is a major determinant in interactions between WCS358 and WCS374 in the rhizosphere. Moreover, our findings support the common assumption that cloning of siderophore receptor genes from one Pseudomonas strain into another can confer a competitive advantage in interactions in the rhizosphere. Interactions between WCS358 and the selected indigenous rhizosphere isolates, however, indicate that other traits also contribute to the rhizosphere competence of fluorescent Pseudomonas spp.Key words: siderophore, siderophore receptors, root colonization, fluorescent Pseudomonas.

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Jjemba, P. K., and Martin Alexander. "Possible determinants of rhizosphere competence of bacteria." Soil Biology and Biochemistry 31, no. 4 (April 1999): 623–32. http://dx.doi.org/10.1016/s0038-0717(98)00168-0.

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Dheeman, Shrivardhan, Nitin Baliyan, Ramesh Chandra Dubey, Dinesh Kumar Maheshwari, Sandeep Kumar, and Lei Chen. "Combined effects of rhizo-competitive rhizosphere and non-rhizosphere Bacillus in plant growth promotion and yield improvement of Eleusine coracana (Ragi)." Canadian Journal of Microbiology 66, no. 2 (February 2020): 111–24. http://dx.doi.org/10.1139/cjm-2019-0103.

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This study emphasizes the beneficial role of rhizo-competitive Bacillus spp. isolated from rhizospheric and non-rhizospheric soil in plant growth promotion and yield improvement via nitrogen fixation and biocontrol of Sclerotium rolfsii causing foot rot disease in Eleusine coracana (Ragi). The selection of potent rhizobacteria was based on plant-growth-promoting attributes using Venn set diagram and Bonitur scale. Bacillus pumilus MSTA8 and Bacillus amyloliquefaciens MSTD26 were selected because they were effective in root colonization, rhizosphere competence, and biofilm formation using root exudates of E. coracana L. rich with carbohydrates, proteins, and amino acids. The relative chemotaxis index of the isolates expressed the invasive behavior of the rhizosphere. During pot and field trials, the consortium of the rhizobacteria in a vermiculite carrier increased the grain yield by 37.87%, with a significant harvest index of 16.45. Soil analysis after the field trial revealed soil reclamation potentials to manage soil nutrition and fertility. Both indexes ensured crop protection and production in eco-safe ways and herald commercialization of Bacillus bio-inoculant for improvement in crop production and disease management of E. coracana.

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Pathania, Priyanka, Ranjana Bhatia, and Madhu Khatri. "Cross-competence and affectivity of maize rhizosphere bacteria Bacillus sp. MT7 in tomato rhizosphere." Scientia Horticulturae 272 (October 2020): 109480. http://dx.doi.org/10.1016/j.scienta.2020.109480.

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Bankhead, Stacey Blouin, Linda S. Thomashow, and David M. Weller. "Rhizosphere Competence of Wild-Type and Genetically Engineered Pseudomonas brassicacearum Is Affected by the Crop Species." Phytopathology® 106, no. 6 (June 2016): 554–61. http://dx.doi.org/10.1094/phyto-09-15-0244-r.

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2,4-Diacetylphloroglucinol (2,4-DAPG)-producing Pseudomonas brassicacearum Q8r1-96 is a highly effective biocontrol agent of take-all disease of wheat. Strain Z30-97, a recombinant derivative of Q8r1-96 containing the phzABCDEFG operon from P. synxantha (formerly P. fluorescens) 2-79 inserted into its chromosome, also produces phenazine-1-carboxylic acid. Rhizosphere population sizes of Q8r1-96, Z30-97, and 2-79, introduced into the soil, were assayed during successive growth cycles of barley, navy bean, or pea under controlled conditions as a measure of the impact of crop species on rhizosphere colonization of each strain. In the barley rhizosphere, Z30-96 colonized less that Q8r1-96 when they were introduced separately, and Q8r1-96 out-competed Z30-96 when the strains were introduced together. In the navy bean rhizosphere, Q8r1-96 colonized better than Z30-97 when the strains were introduced separately. However, both strains had similar population densities when introduced together. Strain Q8r1-96 and Z30-97 colonized the pea rhizosphere equally well when each strain was introduced separately, but Z30-97 out-competed Q8r1-96 when they were introduced together. To our knowledge, this is the first report of a recombinant biocontrol strain of Pseudomonas spp. gaining rhizosphere competitiveness on a crop species. When assessing the potential fate of and risk posed by a recombinant Pseudomonas sp. in soil, both the identity of the introduced genes and the crop species colonized by the recombinant strain need to be considered.

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Mavrodi, D. V., O. V. Mavrodi, B. B. McSpadden-Gardener, B. B. Landa, D. M. Weller, and L. S. Thomashow. "Identification of Differences in Genome Content among phlD-Positive Pseudomonas fluorescens Strains by Using PCR-Based Subtractive Hybridization." Applied and Environmental Microbiology 68, no. 10 (October 2002): 5170–76. http://dx.doi.org/10.1128/aem.68.10.5170-5176.2002.

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ABSTRACT Certain 2,4-diacetylphloroglucinol-producing strains of Pseudomonas fluorescens colonize roots and suppress soilborne diseases more effectively than others from which they are otherwise phenotypically almost indistinguishable. We recovered DNA fragments present in the superior colonizer P. fluorescens Q8r1-96 but not in the less rhizosphere-competent strain Q2-87. Of the open reading frames in 32 independent Q8r1-96-specific clones, 1 was similar to colicin M from Escherichia coli, 3 resembled known regulatory proteins, and 28 had no significant match with sequences of known function. Seven clones hybridized preferentially to DNA from strains with superior rhizosphere competence, and sequences in two others were highly expressed in vitro and in the rhizosphere.

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13

Sivan, A., and G. E. Harman. "Improved rhizosphere competence in a protoplast fusion progeny of Trichoderma harzianum." Journal of General Microbiology 137, no. 1 (January 1, 1991): 23–29. http://dx.doi.org/10.1099/00221287-137-1-23.

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Landa, Blanca B., Dmitri M. Mavrodi, Linda S. Thomashow, and David M. Weller. "Interactions Between Strains of 2,4-Diacetylphloroglucinol-Producing Pseudomonas fluorescens in the Rhizosphere of Wheat." Phytopathology® 93, no. 8 (August 2003): 982–94. http://dx.doi.org/10.1094/phyto.2003.93.8.982.

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Strains of fluorescent Pseudomonas spp. that produce the antibiotic 2,4-diacetylphoroglucinol (2,4-DAPG) are among the most effective rhizobacteria controlling diseases caused by soilborne pathogens. The genotypic diversity that exists among 2,4-DAPG producers can be exploited to improve rhizosphere competence and biocontrol activity. Knowing that D-genotype 2,4-DAPG-producing strains are enriched in some take-all decline soils and that P. fluorescens Q8r1-96, a representative D-genotype strain, as defined by whole-cell repetitive sequence-based polymerase chain reaction (rep-PCR) with the BOXA1R primer, is a superior colonizer of wheat roots, we analyzed whether the exceptional rhizosphere competence of strain Q8r1-96 on wheat is characteristic of other D-genotype isolates. The rhizosphere population densities of four D-genotype strains and a K-genotype strain introduced individually into the soil were significantly greater than the densities of four strains belonging to other genotypes (A, B, and L) and remained above log 6.8 CFU/g of root over a 30-week cycling experiment in which wheat was grown for 10 successive cycles of 3 weeks each. We also explored the competitive interactions between strains of different genotypes inhabiting the same soil or rhizosphere when coinoculated into the soil. Strain Q8r1-96 became dominant in the rhizosphere and in nonrhizosphere soil during a 15-week cycling experiment when mixed in a 1:1 ratio with either strain Pf-5 (A genotype), Q2-87 (B genotype), or 1M1-96 (L genotype). Furthermore, the use of the de Wit replacement series demonstrated a competitive disadvantage for strain Q2-87 or strong antagonism by strain Q8r1-96 against Q2-87 in the wheat rhizosphere. Amplified rDNA restriction analysis and sequence analysis of 16S rDNA showed that species of Arthrobacter, Chryseobacterium, Flavobacterium, Massilia, Microbacterium, and Ralstonia also were enriched in culturable populations from the rhizosphere of wheat at the end of a 30-week cycling experiment in the presence of 2,4-DAPG producers. Identifying the interactions among 2,4-DAPG producers and with other indigenous bacteria in the wheat rhizosphere will help to elucidate the variability in biocontrol efficacy of introduced 2,4-DAPG producers and fluctuations in the robustness of take-all suppressive soils.

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Adesina, Modupe F., Rita Grosch, Antje Lembke, Tzenko D. Vatchev, and Kornelia Smalla. "In vitro antagonists of Rhizoctonia solani tested on lettuce: rhizosphere competence, biocontrol efficiency and rhizosphere microbial community response." FEMS Microbiology Ecology 69, no. 1 (July 2009): 62–74. http://dx.doi.org/10.1111/j.1574-6941.2009.00685.x.

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Pava-Ripoll, Monica, Claudia Angelini, Weiguo Fang, Sibao Wang, Francisco J. Posada, and Raymond St Leger. "The rhizosphere-competent entomopathogen Metarhizium anisopliae expresses a specific subset of genes in plant root exudate." Microbiology 157, no. 1 (January 1, 2011): 47–55. http://dx.doi.org/10.1099/mic.0.042200-0.

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Metarhizium anisopliae and Beauveria bassiana are ubiquitous insect pathogens and possible plant symbionts, as some strains are endophytic or colonize the rhizosphere. We evaluated 11 strains of M. anisopliae and B. bassiana, and two soil saprophytes (the non-rhizospheric Aspergillus niger and the rhizosphere-competent Trichoderma harzianum) for their ability to germinate in bean root exudates (REs). Our results showed that some generalist strains of M. anisopliae were as good at germinating in RE as T. harzianum, although germination rates of the specialized acridid pathogen Metarhizium acridum and the B. bassiana strains were significantly lower. At RE concentrations of <1 mg ml−1, M. anisopliae strain ARSEF 2575 showed higher germination rates than T. harzianum. Microarrays showed that strain 2575 upregulated 29 genes over a 12 h period in RE. A similar number of genes (21) were downregulated. Upregulated genes were involved in carbohydrate metabolism, lipid metabolism, cofactors and vitamins, energy metabolism, proteolysis, extracellular matrix/cell wall proteins, transport proteins, DNA synthesis, the sexual cycle and stress response. However, 41.3 % of the upregulated genes were hypothetical or orphan sequences, indicating that many previously uncharacterized genes have functions related to saprophytic survival. Genes upregulated in response to RE included the subtilisin Pr1A, which is also involved in pathogenicity to insects. However, the upregulated Mad2 adhesin specifically mediates adhesion to plant surfaces, demonstrating that M. anisopliae has genes for rhizosphere competence that are induced by RE.

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Kolton, Max, Omer Frenkel, Yigal Elad, and Eddie Cytryn. "Potential Role of Flavobacterial Gliding-Motility and Type IX Secretion System Complex in Root Colonization and Plant Defense." Molecular Plant-Microbe Interactions® 27, no. 9 (September 2014): 1005–13. http://dx.doi.org/10.1094/mpmi-03-14-0067-r.

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Members of the Flavobacterium genus are often highly abundant in the rhizosphere. Nevertheless, the physiological characteristics associated with their enhanced rhizosphere competence are currently an enigma. Flavobacteria possess a unique gliding-motility complex that is tightly associated with a recently characterized Bacteroidetes-specific type IX protein secretion system, which distinguishes them from the rest of the rhizosphere microbiome. We hypothesize that proper functionality of this complex may confer a competitive advantage in the rhizosphere. To test this hypothesis, we constructed mutant and complement root-associated flavobacterial variants with dysfunctional secretion and gliding motility, and tested them in a series of in planta experiments. These mutants demonstrated significantly lower rhizosphere persistence (approximately 10-fold), plant root colonization (approximately fivefold), and seed adhesion capacity (approximately sevenfold) than the wild-type strains. Furthermore, the biocontrol capacity of the mutant strain toward foliar-applied Clavibacter michiganensis was significantly impaired relative to the wild-type strain, suggesting a role of the gliding and secretion complex in plant protection. Collectively, these results provide an initial link between the high abundance of flavobacteria in the rhizosphere and their unique physiology, indicating that the flavobacterial gliding-motility and secretion complex may play a central role in root colonization and plant defense.

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El-Tarabily, Khaled A. "Rhizosphere-competent isolates of streptomycete and non-streptomycete actinomycetes capable of producing cell-wall-degrading enzymes to controlPythium aphanidermatumdamping-off disease of cucumber." Canadian Journal of Botany 84, no. 2 (February 2006): 211–22. http://dx.doi.org/10.1139/b05-153.

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Fifty-eight streptomycete and 35 non-streptomycete actinomycetes were isolated from cucumber rhizosphere soil. These isolates were screened for the production of cell-wall-degrading enzymes using mycelial ( Pythium aphanidermatum (Edson) Fitzp.) fragment agar. Eighteen promising isolates were screened for their competence as root colonizers. Eight isolates showing exceptional rhizosphere competence significantly inhibited, in vitro, P. aphanidermatum, the causal agent of postemergence damping-off of cucumber ( Cucumis sativus L.) seedlings. The four most inhibitory isolates ( Actinoplanes philippinensis Couch, Microbispora rosea Nonomura and Ohara, Micromonospora chalcea (Foulerton) Ørskov, and Streptomyces griseoloalbus (Kudrina) Pridham et al.) produced in vitro β-1,3-, β-1,4-, and β-1,6-glucanases and caused lysis of P. aphanidermatum hyphae. None of these produced volatile inhibitors or siderophores. Only S. griseoloalbus produced diffusible inhibitory metabolites, whilst A. philippinensis and Micromonospora chalcea parasitized the oospores of P. aphanidermatum. These four isolates were subsequently tested in the greenhouse, individually or as a mixture, for their ability to suppress damping-off of cucumber seedlings in soil with or without cellulose amendment. The treatment, which included all four isolates in soil amended with cellulose, was significantly superior to all other treatments in suppressing damping-off and was nearly as good as the metalaxyl treatment. Results show that there is a potential to use a mixture of antagonistic rhizosphere-competent actinomycetes along with cellulose amendment rather than fungicides for the field management of this disease. This is the first study that has involved the screening of rhizosphere-competent non-streptomycete actinomycetes capable of producing cell-wall-degrading enzymes, for the management of Pythium diseases.

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Bach, Evelise, Guilherme Dubal dos Santos Seger, Gabriela de Carvalho Fernandes, Bruno Brito Lisboa, and Luciane Maria Pereira Passaglia. "Evaluation of biological control and rhizosphere competence of plant growth promoting bacteria." Applied Soil Ecology 99 (March 2016): 141–49. http://dx.doi.org/10.1016/j.apsoil.2015.11.002.

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Lettice, Eoin P., and Peter W. Jones. "Evaluation of rhizobacterial colonisation and the ability to induce Globodera pallida hatch." Nematology 17, no. 2 (2015): 203–12. http://dx.doi.org/10.1163/15685411-00002863.

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Three bacterial isolates, SB13 (Acinetobacter sp.), SB14 (Arthrobacter sp.) and SB15 (Bacillus sp.), were previously isolated from the rhizosphere of sugar beet (Beta vulgaris ssp. vulgaris) plants and shown to increase hatch of potato cyst nematodes in vitro. In this study, the three isolates were assayed for rhizosphere competence. Each isolate was applied to seeds at each of four concentrations (105-108 CFU ml−1) and the inoculated seeds were planted in plastic microcosms containing coarse sand. All three isolates were shown to colonise the rhizosphere, although to differing degrees, with the higher inoculation densities providing significantly better colonisation. The isolates increased sugar beet root and shoot dry weight. Isolates SB14 and SB15 were analysed for their ability to induce in vivo hatch of Globodera pallida in non-sterile soil planted with sugar beet. After 4 and 6 weeks, both isolates had induced significantly greater percentage hatch compared to controls.

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Carvalho, Daniel Diego Costa, Sueli Corrêa Marques de Mello, Murillo Lobo Júnior, and Alaerson Maia Geraldine. "Biocontrol of seed pathogens and growth promotion of common bean seedlings by Trichoderma harzianum." Pesquisa Agropecuária Brasileira 46, no. 8 (August 2011): 822–28. http://dx.doi.org/10.1590/s0100-204x2011000800006.

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The objective of this work was to evaluate isolates of Trichoderma harzianum regarding biocontrol of common bean seed-borne pathogens, plant growth promotion, and rhizosphere competence. Five isolates of T. harzianum were evaluated and compared with commercial isolate (Ecotrich), Carboxin+Thiram, and an absolute control. Bean seeds of the cultivar Jalo Precoce, contaminated with Aspergillus, Cladosporium, and Sclerotinia sclerotiorum, were microbiolized with antagonists, and seed health tests were carried out. Isolates were evaluated on autoclaved substrate and in field conditions. Ten days after sowing (DAS), plant length was measured. To test rhizosphere competence, isolates were applied in boxes containing autoclaved washed sand, and root colonization was evaluated at 10 DAS, using five plants per box. The most effective isolates in the seed health tests were: CEN287 and CEN289 to control Aspergillus; the commercial isolate to control Cladosporium; and CEN287 and CEN316 to control S. sclerotiorum. Isolates CEN289 and CEN290 promoted bean growth in greenhouse and field. Seed treatment with T. harzianum reduces the incidence of Aspergillus, Cladosporium, and S. sclerotiorum in 'Jalo Precoce' common bean seeds.

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Ahmad, Jaleed S., and Ralph Baker. "Growth of rhizosphere-competent mutants of Trichoderma harzianum on carbon substrates." Canadian Journal of Microbiology 34, no. 6 (June 1, 1988): 807–14. http://dx.doi.org/10.1139/m88-137.

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When the strains of Trichoderma harzianum were grown in Czapek-Dox broth without saccharose with cotton linters, microcrystalline cellulose, wood cellulose, or xylan as a sole source of carbon, the rhizosphere-competent mutants produced significantly higher biomass than the rhizosphere-incompetent wild types. Both mutants and wild types did not readily grow on glucose, galactose, cellobiose, or xylose as sole source of carbon. The mutants, T-95 and T-12B, produced significantly higher biomass when grown on complex carbohydrates with added simple sugars. The wild types did not produce significantly greater biomass when both simple and complex sugars were the carbon sources than when either substrate was used alone. The ability of the mutants to grow more rapidly on complex carbon substrates (typical of those found on root surfaces) than their wild-type parents, and to increase biomass when simple sugars were added along with the cellulose substrate could be of ecological significance and a characteristic of rhizosphere competence.

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Milus, Eugene A., and Craig S. Rothrock. "Rhizosphere colonization of wheat by selected soil bacteria over diverse environments." Canadian Journal of Microbiology 39, no. 3 (March 1, 1993): 335–41. http://dx.doi.org/10.1139/m93-047.

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The ability to colonize the rhizosphere is essential for bacteria to function as biological control agents for soil-borne plant pathogens. Eight bacterial strains reported to colonize wheat roots, inhibit root pathogens, and (or) improve wheat growth and yield were applied to wheat seeds that were planted in fumigated and nonfumigated soil in the 1990 and 1991 growing seasons at two locations in Arkansas. Rhizosphere population sizes were highly correlated with population sizes on seeds. Bacillus subtilis strain D-39Sr colonized roots as well in nonfumigated as in fumigated soil, and the other seven strains had rhizosphere populations 0.3 to 1.1 log units higher in fumigated soil. Pseudomonas fluorescens strain 2-79R was one of the best colonizers, and Streptomyces strain D-185S was the poorest. The greatest difference among strains was for relative colonization ability of crown roots in the spring. All strains except Streptomyces strain D-185S appear to have broad adaptation to colonize wheat roots and are able to compete with soil microflora for colonization sites. This research indicates that it is possible to select bacteria in the genera Bacillus, Pseudomonas, or Xanthomonas that will colonize roots well over diverse environments. Rhizosphere colonization by these strains was not associated with disease suppression or enhanced plant growth or yield.Key words: biological control, rhizosphere competence, wheat, Triticum aestivum.

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TOYOTA, KOKI, CHIKAYO HIRAIWA (NOJIRI), and MAKOTO KIMURA. "Phenotypic Characterization of a Mutant of Burkholderia cepacia MRT11 Defective in Rhizosphere Competence." Microbes and environments 14, no. 4 (1999): 201–8. http://dx.doi.org/10.1264/jsme2.14.201.

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Barret, Matthieu, John P. Morrissey, and Fergal O’Gara. "Functional genomics analysis of plant growth-promoting rhizobacterial traits involved in rhizosphere competence." Biology and Fertility of Soils 47, no. 7 (July 26, 2011): 729–43. http://dx.doi.org/10.1007/s00374-011-0605-x.

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Ghiglione, Jean-FranÃ¯Â¿Â½ois, FranÃ¯Â¿Â½ois Gourbiere, Patrick Potier, Laurent Philippot, and Robert Lensi. "Role of Respiratory Nitrate Reductase in Ability ofPseudomonas fluorescens YT101 To Colonize the Rhizosphere of Maize." Applied and Environmental Microbiology 66, no. 9 (September 1, 2000): 4012–16. http://dx.doi.org/10.1128/aem.66.9.4012-4016.2000.

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ABSTRACT Selection of the denitrifying community by plant roots (i.e., increase in the denitrifier/total heterotroph ratio in the rhizosphere) has been reported by several authors. However, very few studies to evaluate the role of the denitrifying function itself in the selection of microorganisms in the rhizosphere have been performed. In the present study, we compared the rhizosphere survival of the denitrifyingPseudomonas fluorescens YT101 strain with that of its isogenic mutant deficient in the ability to synthesize the respiratory nitrate reductase, coinoculated in nonplanted or planted soil. We demonstrated that under nonlimiting nitrate conditions, the denitrifying wild-type strain had an advantage in the ability to colonize the rhizosphere of maize. Investigations of the effect of the inoculum characteristics (density of the total inoculum and relative proportions of mutant and wild-type strains) on the outcome of the selection demonstrated that the selective effect of the plant was expressed only during the phase of bacterial multiplication and that the intensity of selection was dependent on the magnitude of this phase. Moreover, application of the de Wit replacement series technique to our results suggests that the advantage of the wild-type strain was maximal when the ratio between the two strains in the inoculum was close to 1:1. This work constitutes the first direct demonstration that the presence of a functional structural gene encoding the respiratory nitrate reductase confers higher rhizosphere competence to a microorganism.

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MoÃ«nne-Loccoz, Yvan, Brendan McHugh, Peter M. Stephens, Fiona I. McConnell, Jeremy D. Glennon, David N. Dowling, and Fergal O'Gara. "Rhizosphere competence of fluorescent Pseudomonas sp. B24 genetically modified to utilise additional ferric siderophores." FEMS Microbiology Ecology 19, no. 4 (April 1996): 215–25. http://dx.doi.org/10.1111/j.1574-6941.1996.tb00214.x.

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McLean, K. L., J. Swaminathan, C. M. Frampton, J. S. Hunt, H. J. Ridgway, and A. Stewart. "Effect of formulation on the rhizosphere competence and biocontrol ability of Trichoderma atroviride C52." Plant Pathology 54, no. 2 (April 2005): 212–18. http://dx.doi.org/10.1111/j.1365-3059.2005.01158.x.

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Nian, Hong Juan, Jie Zhang, Shuo Liu, Fu Ping Song, and Da Fang Huang. "Effect of bacteriaphage and exopolysaccharide on root colonization and rhizosphere competence by Pseudomonas fluorescens." Annals of Microbiology 60, no. 2 (May 1, 2010): 369–72. http://dx.doi.org/10.1007/s13213-010-0050-3.

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Moënne-Loccoz, Y. "Rhizosphere competence of fluorescent Pseudomonas sp. B24 genetically modified to utilise additional ferric siderophores." FEMS Microbiology Ecology 19, no. 4 (April 1996): 215–25. http://dx.doi.org/10.1016/0168-6496(96)00007-4.

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Singh, Randeep, Aditi Sharma, and A. K. Gupta. "Rhizosphere competence of native Rhizobium rhizogenes strain and its use in management of crown gall." Journal of Applied and Natural Science 9, no. 3 (September 1, 2017): 1772–81. http://dx.doi.org/10.31018/jans.v9i3.1437.

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Native Rhizobium rhizogenes strain UHFBA-212 [141/1A (NCBI: KC488174)]was isolated from rhizosphere soil of peach nursery plant of wild peach collected from Himachal Pradesh. In addition to this,159 isolates were also collected and were screened in vitro for their biocontrol potential against Agrobacterium tumefaciens. Out of these strain, UHFBA-212 showed maximum zone of inhibition i.e. 4.16 and 3.57cm without and after exposure to chloroform against C58.Sequence analysis (16SrDNA) of the strain showed nucleotide homology similar to Rhizobium sp. Amplification of total genomic DNA of the strain with Vir D2 andipt primers didn’t showed amplification with these virulence genes suggesting the absence of tumorigenic factors. In the field conditions, maximum population (329.33x106 cfu/g of soil) was observed in antibiotic resistant mutant of R. rhizogenes strain K84 applied on cherry rootstock Colt followed by 285.33 (x 106 ) cfu/g of soil in UHFBA-212 after 9 months at the time of uprooting of plants when applied alone as root dip. Minimum incidence of crown gall (2.00%) was observed in strain UHFBA- 212 co inoculated with strain C58 as seed treatment on behmi seeds. The data on population indices in rhizosphere and incidence of crown gall further suggested that for better management of disease R. Rhizogenes isolates should be either equal or more in population than that of A. tumefaciens isolates. Strain UHFBA-212 controls crown gall as effectively as strain K84 and can be exploited against tumorigenic isolates under field conditions.

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Ben Saad, Marwa, Myriam Ben Said, Isabel Sanz-Sáez, Olga Sánchez, Jordi Morató, Latifa Bousselmi, and Ahmed Ghrabi. "Enhancement of rhizocompetence in pathogenic bacteria removal of a constructed wetland system." Water Science and Technology 79, no. 2 (January 15, 2019): 251–59. http://dx.doi.org/10.2166/wst.2019.028.

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Abstract The main goal of the present study was to enhance the rhizobacterium potential in a horizontal subsurface flow constructed wetland system planted with Phragmites australis, through environmentally friendly biological approaches. The bioinoculation of antagonist bacteria has been used to promote higher rhizosphere competence and improve pathogenic bacteria removal from wastewater. The experiment was performed both with single and sequential bioinoculation. The results showed that strain PFH1 played an active role in pathogenic bacteria removal, remarkably improving inactivation kinetics of the pathogenic tested bacterium Salmonella typhi in the plant rhizosphere. The single bioinoculation of selected bacteria into the rhizosphere of P. australis improved the kinetics of S. typhi inactivation by approximately 1 U-Log10 (N/N0) (N is the number of viable cultured bacteria at time t, N0 is the number of viable and cultivable bacteria at time t0) compared to the control. By a series of multi-bioinoculations, the enhancement of pathogenic bacteria reduction compared to the inhibition rate in the pilot-scale control was of 2 U-Log10(N/N0). These findings suggested that this strain represents a promising candidate to enhance water purification in constructed wetlands.

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Schreiter, Susanne, Martin Sandmann, Kornelia Smalla, and Rita Grosch. "Soil Type Dependent Rhizosphere Competence and Biocontrol of Two Bacterial Inoculant Strains and Their Effects on the Rhizosphere Microbial Community of Field-Grown Lettuce." PLoS ONE 9, no. 8 (August 6, 2014): e103726. http://dx.doi.org/10.1371/journal.pone.0103726.

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Pappu, Lalitha. "Enhanced rhizosphere competence of Trichoderma viride grown in solid state fermentation on corn cob residue." Archives of Phytopathology and Plant Protection 51, no. 9-10 (June 15, 2018): 505–29. http://dx.doi.org/10.1080/03235408.2018.1490236.

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Landa, Blanca B., Olga V. Mavrodi, Jos M. Raaijmakers, Brian B. McSpadden Gardener, Linda S. Thomashow, and David M. Weller. "Differential Ability of Genotypes of 2,4-Diacetylphloroglucinol-Producing Pseudomonas fluorescens Strains To Colonize the Roots of Pea Plants." Applied and Environmental Microbiology 68, no. 7 (July 2002): 3226–37. http://dx.doi.org/10.1128/aem.68.7.3226-3237.2002.

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ABSTRACT Indigenous populations of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing fluorescent Pseudomonas spp. that occur naturally in suppressive soils are an enormous resource for improving biological control of plant diseases. Over 300 isolates of 2,4-DAPG-producing fluorescent Pseudomonas spp. were isolated from the rhizosphere of pea plants grown in soils that had undergone pea or wheat monoculture and were suppressive to Fusarium wilt or take-all, respectively. Representatives of seven genotypes, A, D, E, L, O, P, and Q, were isolated from both soils and identified by whole-cell repetitive sequence-based PCR (rep-PCR) with the BOXA1R primer, increasing by three (O, P, and Q) the number of genotypes identified previously among a worldwide collection of 2,4-DAPG producers. Fourteen isolates representing eight different genotypes were tested for their ability to colonize the rhizosphere of pea plants. Population densities of strains belonging to genotypes D and P were significantly greater than the densities of other genotypes and remained above log 6.0 CFU (g of root)−1 over the entire 15-week experiment. Genetic profiles generated by rep-PCR or restriction fragment length polymorphism analysis of the 2,4-DAPG biosynthetic gene phlD were predictive of the rhizosphere competence of the introduced 2,4-DAPG-producing strains.

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McLean, K. L., S. L. Dodd, B. E. Sleight, R. A. Hill, and A. Stewart. "Comparison of the behaviour of a transformed hygromycin resistant strain of Trichoderma atroviride (M1057hygR) with the wildtype strain (M1057)." New Zealand Plant Protection 57 (August 1, 2004): 72–76. http://dx.doi.org/10.30843/nzpp.2004.57.6892.

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The biocontrol isolate Trichoderma atroviride M1057 and a transformed hygromycin resistant biotype (M1057hygR) were compared using biological control rhizosphere competence and antibiosis studies to determine whether the transformed biotype performed in a similar manner to the wildtype strain In an onion growth chamber trial using soil naturally infested with the onion white rot pathogen Sclerotium cepivorum there was no significant difference (P>005) in the level of disease control given by the two T atroviride strains Similarly populations of T atroviride M1057 and M1057hygR were equivalent (P>005) in the rhizosphere of onion seedlings There was no significant difference (P>005) between the mycelial growth rates of S cepivorum when grown on agar amended with culture filtrate of T atroviride M1057 and M1057hygR Thus T atroviride M1057hygR has similar biological attributes to the wildtype isolate and can be used in future field studies looking at the population ecology of the biological control agent

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Björkman, Thomas, Lisa Blanchard, and Gary E. Harman. "The Effect of Rhizosphere Competence on Colonization of Sweet Corn Roots by Biocontrol Fungi in Differing Soils." HortScience 33, no. 3 (June 1998): 526b—526. http://dx.doi.org/10.21273/hortsci.33.3.526b.

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To be effective, biocontrol agents, fungi need to colonize roots under a wide range of conditions. The ability do so is called rhizosphere competence. A common beneficial fungus, Trichoderma harzianum, has been bred to produce a new strain, T-22, that has exceptionally high rhizosphere competence. In field experiments, we have demonstrated that T-22 was resistant to edaphic conditions that reduce colonization by indigenous Trichoderma species, so that it can provide protection against root pathogens. Well-drained sand, stone or gravel soils supported lower populations of wild Trichoderma than did loams (100.5 vs 10 3.3 cfu/g), but populations of T-22 were high in all soils (>104 cfu/g). In a multivariate analysis of soil characteristics affecting colonization, only soils with low Ca and low pH had reduced populations. No other measured soil characteristics were correlated with colonization. When sown in the field at different initial soil temperatures ranging from 10 to 27 °C, T-22 populations were unaffected by temperature, having a population from 104.6 to 105.4 cfu/g. Indigenous strains were 103 in cold soils, peaked at 104 at 15 °C, declining in later sowings due to higher biological competition. Differences in microbial competition had little effect. Roots were equally colonized in the differing soil microflora in three management systems at the Rodale Farming Systems Trial. Invading an existing soil microbial community is the most difficult thing to achieve with a biocontrol organism. These data show that T-22 is the first to consistently do so.

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Yan, Y., J. Yang, Y. Dou, M. Chen, S. Ping, J. Peng, W. Lu, et al. "Nitrogen fixation island and rhizosphere competence traits in the genome of root-associated Pseudomonas stutzeri A1501." Proceedings of the National Academy of Sciences 105, no. 21 (May 21, 2008): 7564–69. http://dx.doi.org/10.1073/pnas.0801093105.

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Weller, David M. "Pseudomonas Biocontrol Agents of Soilborne Pathogens: Looking Back Over 30 Years." Phytopathology® 97, no. 2 (February 2007): 250–56. http://dx.doi.org/10.1094/phyto-97-2-0250.

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Pseudomonas spp. are ubiquitous bacteria in agricultural soils and have many traits that make them well suited as biocontrol agents of soilborne pathogens. Tremendous progress has been made in characterizing the process of root colonization by pseudomonads, the biotic and abiotic factors affecting colonization, bacterial traits and genes contributing to rhizosphere competence, and the mechanisms of pathogen suppression. This review looks back over the last 30 years of Pseudomonas biocontrol research and highlights key studies, strains, and findings that have had significant impact on shaping our current understanding of biological control by bacteria and the direction of future research.

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Raaijmakers, Jos M., and David M. Weller. "Exploiting Genotypic Diversity of 2,4-Diacetylphloroglucinol-Producing Pseudomonas spp.: Characterization of Superior Root-Colonizing P. fluorescensStrain Q8r1-96." Applied and Environmental Microbiology 67, no. 6 (June 1, 2001): 2545–54. http://dx.doi.org/10.1128/aem.67.6.2545-2554.2001.

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ABSTRACT The genotypic diversity that occurs in natural populations of antagonistic microorganisms provides an enormous resource for improving biological control of plant diseases. In this study, we determined the diversity of indigenous 2,4-diacetylphloroglucinol (DAPG)-producingPseudomonas spp. occurring on roots of wheat grown in a soil naturally suppressive to take-all disease of wheat. Among 101 isolates, 16 different groups were identified by random amplified polymorphic DNA (RAPD) analysis. One RAPD group made up 50% of the total population of DAPG-producing Pseudomonas spp. Both short- and long-term studies indicated that this dominant genotype, exemplified by P. fluorescens Q8r1-96, is highly adapted to the wheat rhizosphere. Q8r1-96 requires a much lower dose (only 10 to 100 CFU seed−1 or soil−1) to establish high rhizosphere population densities (107 CFU g of root−1) than Q2-87 and 1M1-96, two genotypically different, DAPG-producing P. fluorescens strains. Q8r1-96 maintained a rhizosphere population density of approximately 105 CFU g of root−1 after eight successive growth cycles of wheat in three different, raw virgin soils, whereas populations of Q2-87 and 1M1-96 dropped relatively quickly after five cycles and were not detectable after seven cycles. In short-term studies, strains Q8r1-96, Q2-87, and 1M1-96 did not differ in their ability to suppress take-all. After eight successive growth cycles, however, Q8r1-96 still provided control of take-all to the same level as obtained in the take-all suppressive soil, whereas Q2-87 and 1M1-96 gave no control anymore. Biochemical analyses indicated that the superior rhizosphere competence of Q8r1-96 is not related to in situ DAPG production levels. We postulate that certain rhizobacterial genotypes have evolved a preference for colonization of specific crops. By exploiting diversity of antagonistic rhizobacteria that share a common trait, biological control can be improved significantly.

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Mirleau, Pascal, Laurent Philippot, Thérèse Corberand, and Philippe Lemanceau. "Involvement of Nitrate Reductase and Pyoverdine in Competitiveness of Pseudomonas fluorescens Strain C7R12 in Soil." Applied and Environmental Microbiology 67, no. 6 (June 1, 2001): 2627–35. http://dx.doi.org/10.1128/aem.67.6.2627-2635.2001.

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ABSTRACT Involvement of nitrate reductase and pyoverdine in the competitiveness of the biocontrol strain Pseudomonas fluorescens C7R12 was determined, under gnotobiotic conditions, in two soil compartments (bulk and rhizosphere soil), with the soil being kept at two different values of matric potential (−1 and −10 kPa). Three mutants affected in the synthesis of either the nitrate reductase (Nar−), the pyoverdine (Pvd−), or both (Nar− Pvd−) were used. The Nar− and Nar− Pvd− mutants were obtained by site-directed mutagenesis of the wild-type strain and of the Pvd− mutant, respectively. The selective advantage given by nitrate reductase and pyoverdine to the wild-type strain was assessed by measuring the dynamic of each mutant-to-total-inoculant (wild-type strain plus mutant) ratio. All three mutants showed a lower competitiveness than the wild-type strain, indicating that both nitrate reductase and pyoverdine are involved in the fitness of P. fluorescens C7R12. The double mutant presented the lowest competitiveness. Overall, the competitive advantages given to C7R12 by nitrate reductase and pyoverdine were similar. However, the selective advantage given by nitrate reductase was more strongly expressed under conditions of lower aeration (−1 kPa). In contrast, the selective advantage given by nitrate reductase and pyoverdine did not differ in bulk and rhizosphere soil, indicating that these bacterial traits are not specifically involved in the rhizosphere competence but rather in the saprophytic ability of C7R12 in soil environments.

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López-Berges, Manuel S., Javier Capilla, David Turrà, Lukas Schafferer, Sandra Matthijs, Christoph Jöchl, Pierre Cornelis, Josep Guarro, Hubertus Haas, and Antonio Di Pietro. "HapX-Mediated Iron Homeostasis Is Essential for Rhizosphere Competence and Virulence of the Soilborne Pathogen Fusarium oxysporum." Plant Cell 24, no. 9 (September 2012): 3805–22. http://dx.doi.org/10.1105/tpc.112.098624.

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Shidore, Teja, Theresa Dinse, Johannes Öhrlein, Anke Becker, and Barbara Reinhold-Hurek. "Transcriptomic analysis of responses to exudates reveal genes required for rhizosphere competence of the endophyteAzoarcussp. strain BH72." Environmental Microbiology 14, no. 10 (May 23, 2012): 2775–87. http://dx.doi.org/10.1111/j.1462-2920.2012.02777.x.

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Geetha, S. J., and Sanket J. Joshi. "Engineering Rhizobial Bioinoculants: A Strategy to Improve Iron Nutrition." Scientific World Journal 2013 (2013): 1–15. http://dx.doi.org/10.1155/2013/315890.

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Under field conditions, inoculated rhizobial strains are at a survival disadvantage as compared to indigenous strains. In order to out-compete native rhizobia it is not only important to develop strong nodulation efficiency but also increase their competence in the soil and rhizosphere. Competitive survival of the inoculated strain may be improved by employing strain selection and by genetic engineering of superior nitrogen fixing strains. Iron sufficiency is an important factor determining the survival and nodulation by rhizobia in soil. Siderophores, a class of ferric specific ligands that are involved in receptor specific iron transport into bacteria, constitute an important part of iron acquisition systems in rhizobia and have been shown to play a role in symbiosis as well as in saprophytic survival. Soils predominantly have iron bound to hydroxamate siderophores, a pool that is largely unavailable to catecholate-utilizing rhizobia. Outer membrane receptors for uptake of ferric hydroxamates include FhuA and FegA which are specific for ferrichrome siderophore. Increase in nodule occupancy and enhanced plant growth of thefegAandfhuAexpressing engineered bioinoculants rhizobial strain have been reported. Engineering rhizobia for developing effective bioinoculants with improved ability to utilize heterologous siderophores could provide them with better iron acquisition ability and consequently, rhizospheric stability.

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Hernández-Salmerón, Julie E., Gabriel Moreno-Hagelsieb, and Gustavo Santoyo. "Genome Comparison of Pseudomonas fluorescens UM270 with Related Fluorescent Strains Unveils Genes Involved in Rhizosphere Competence and Colonization." Journal of Genomics 5 (2017): 91–98. http://dx.doi.org/10.7150/jgen.21588.

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Melo, I. S., J. L. Faull, and K. A. Graeme-Cook. "Relationship between in vitro cellulase production of uv-induced mutants of Trichoderma harzianum and their bean rhizosphere competence." Mycological Research 101, no. 11 (November 1997): 1389–92. http://dx.doi.org/10.1017/s0953756297004280.

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Mavrodi, Olga V., Dmitri V. Mavrodi, Amanda A. Park, David M. Weller, and Linda S. Thomashow. "The role of dsbA in colonization of the wheat rhizosphere by Pseudomonas fluorescens Q8r1-96." Microbiology 152, no. 3 (March 1, 2006): 863–72. http://dx.doi.org/10.1099/mic.0.28545-0.

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Certain well-conserved genes in fluorescent Pseudomonas spp. are involved in pathogenic interactions between the bacteria and evolutionarily diverse hosts including plants, insects and vertebrate animals. One such gene, dsbA, encodes a periplasmic disulfide-bond-forming enzyme implicated in the biogenesis of exported proteins and cell surface structures. This study focused on the role of dsbA in Pseudomonas fluorescens Q8r1-96, a biological control strain that produces the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) and is known for its exceptional ability to colonize the roots of wheat and pea. The deduced DsbA protein from Q8r1-96 is similar to other predicted thiol : disulfide interchange proteins and contains a conserved DsbA catalytic site, a pattern associated with the thioredoxin family active site, and a signal peptide and cleavage site. A dsbA mutant of Q8r1-96 exhibited decreased motility and fluorescence, and altered colony morphology; however, it produced more 2,4-DAPG and total phloroglucinol-related compounds and was more inhibitory in vitro to the fungal root pathogen Gaeumannomyces graminis var. tritici than was the parental strain. When introduced separately into a natural soil, Q8r1-96 and the dsbA mutant did not differ in their ability to colonize the rhizosphere of wheat in greenhouse experiments lasting 12 weeks. However, when the two strains were co-inoculated, the parental strain consistently out-competed the dsbA mutant. It was concluded that dsbA does not contribute to the exceptional rhizosphere competence of Q8r1-96, although the dsbA mutation reduces competitiveness when the mutant competes with the parental strain in the same niche in the rhizosphere. The results also suggest that exoenzymes and multimeric cell surface structures are unlikely to have a critical role in root colonization by this strain.

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Nautiyal, C. Shekhar, J. K. Johri, and H. B. Singh. "Survival of the rhizosphere-competent biocontrol strainPseudomonas fluorescensNBRI2650 in the soil and phytosphere." Canadian Journal of Microbiology 48, no. 7 (July 1, 2002): 588–601. http://dx.doi.org/10.1139/w02-054.

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Pseudomonas fluorescens NBRI2650 was isolated after screening 360 bacterial strains from the rhizosphere of chickpea (Cicer arietinum L.) grown in fungal-disease-suppressive field soil. The strain was selected because of its high rhizosphere competence and ability to inhibit the growth of Fusarium oxysporum f.sp. ciceri, Rhizoctonia bataticola, and Pythium sp. under in vitro conditions. Survival and colonization of NBRI2650 in the phytosphere of chickpea, cotton (Gossypium hirsutum L.), cucumber (Cucumis sativus L.), and tomato (Lycopersicon seculentum Mill.) were monitored using a chromosomally located rifampicin-marked mutant P. fluorescens NBRI2650R. The strain showed variable ability to invade and survive in the phytosphere of different plants. Chickpea was used as a tester plant for further work, as it was not invaded by NBRI2650R. The interaction between NBRI2650R and F. oxysporum f.sp. ciceri was studied by both light microscopy and scanning electron microscopy. The lysis of the fungal cell wall by NBRI2650R was clearly demonstrated. Treatment of the chickpea seeds with NBRI2650R in prerelease experiments in the greenhouse using disease-conducive field soils from Jhansi and Kanpur resulted in increased plant growth and did not result in any perturbation of the indigenous microbial community that inhabited the rhizosphere of chickpea compared with nonbacterized seeds. Direct fermentation of diluted NBRI2650R on vermiculite without the need of expensive fermentors offers a reliable process for manufacturing bacterial inoculants in developing countries. Under field conditions, the horizontal and vertical movement of NBRI2650R was restricted to 30 and 60 cm, respectively, and the strain could not survive in the field during the 7 months before the chickpea could be planted for next cropping season. Field trials conducted at Jhansi, Kanpur, and Pantnagar resulted in higher grain yield increase in the bacteria-treated seed compared with the nonbacterized control. Seed and furrow treatment of the two chickpeas ('Radhey' and 'H-208') at Pantnagar resulted in significantly (P = 0.05) greater seedling mortality in nonbacterized seedlings compared with bacterized ones. The seed dry weight and yield for each variety were also significantly higher in bacterized seedlings than in nonbacterized ones. The population of NBRI2650R persisted throughout the growing season of chickpea in the range of 5.46.4 log10CFU/g root.Key words: chickpea, competition, rhizosphere, biocontrol, survival.

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Elshafie, Hazem S., and Ippolito Camele. "An Overview of Metabolic Activity, Beneficial and Pathogenic Aspects of Burkholderia Spp." Metabolites 11, no. 5 (May 17, 2021): 321. http://dx.doi.org/10.3390/metabo11050321.

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Burkholderia is an important bacterial species which has different beneficial effects, such as promoting the plant growth, including rhizosphere competence for the secretion of allelochemicals, production of antibiotics, and siderophores. In addition, most of Burkholderia species have demonstrated promising biocontrol action against different phytopathogens for diverse crops. In particular, Burkholderia demonstrates significant biotechnological potential as a source of novel antibiotics and bioactive secondary metabolites. The current review is concerned with Burkholderia spp. covering the following aspects: discovering, classification, distribution, plant growth promoting effect, and antimicrobial activity of different species of Burkholderia, shedding light on the most important secondary metabolites, their pathogenic effects, and biochemical characterization of some important species of Burkholderia, such as B. cepacia, B. andropogonis, B. plantarii, B. rhizoxinica, B. glumae, B. caryophylli and B. gladioli.

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Nautiyal, C. Shekhar. "Rhizosphere competence of Pseudomonas sp. NBRI9926 and Rhizobium sp. NBRI9513 involved in the suppression of chickpea (Cicerarietinum L.) pathogenic fungi." FEMS Microbiology Ecology 23, no. 2 (January 17, 2006): 145–58. http://dx.doi.org/10.1111/j.1574-6941.1997.tb00398.x.

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Journal articles on the topic 'Rhizosphere competence'

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