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  • 1
    Online Resource
    Online Resource
    Biological Control of Take-All by Fluorescent Pseudomonas spp. from Chinese Wheat Fields
    Scientific Societies ; 2011
    In:  Phytopathology® Vol. 101, No. 12 ( 2011-12), p. 1481-1491
    Details
    In: Phytopathology®, Scientific Societies, Vol. 101, No. 12 ( 2011-12), p. 1481-1491
    Abstract: Take-all disease of wheat caused by the soilborne fungus Gaeumannomyces graminis var. tritici is one of the most important root diseases of wheat worldwide. Bacteria were isolated from winter wheat from irrigated and rainfed fields in Hebei and Jiangsu provinces in China, respectively. Samples from rhizosphere soil, roots, stems, and leaves were plated onto King's medium B agar and 553 isolates were selected. On the basis of in vitro tests, 105 isolates (19% of the total) inhibited G. graminis var. tritici and all were identified as Pseudomonas spp. by amplified ribosomal DNA restriction analysis. Based on biocontrol assays, 13 strains were selected for further analysis. All of them aggressively colonized the rhizosphere of wheat and suppressed take-all. Of the 13 strains, 3 (HC9-07, HC13-07, and JC14-07, all stem endophytes) had genes for the biosynthesis of phenazine-1-carboxylic acid (PCA) but none had genes for the production of 2,4-diacetylphloroglucinol, pyoluteorin, or pyrrolnitrin. High-pressure liquid chromatography (HPLC) analysis of 2-day-old cultures confirmed that HC9-07, HC13-07, and JC14-07 produced PCA but no other phenazines were detected. HPLC quantitative time-of-flight 2 mass-spectrometry analysis of extracts from roots of spring wheat colonized by HC9-07, HC13-07, or Pseudomonas fluorescens 2-79 demonstrated that all three strains produced PCA in the rhizosphere. Loss of PCA production by strain HC9-07 resulted in a loss of biocontrol activity. Analysis of DNA sequences within the key phenazine biosynthesis gene phzF and of 16S rDNA indicated that strains HC9-07, HC13-07, and JC14-07 were similar to the well-described PCA producer P. fluorescens 2-79. This is the first report of 2-79-like bacteria being isolated from Asia.
    Type of Medium: Online Resource
    ISSN: 0031-949X , 1943-7684
    URL: Article
    DOI: 10.1094/PHYTO-04-11-0096
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2011
    detail.hit.zdb_id: 2037027-1
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  • 2
    Online Resource
    Online Resource
    Genetic Diversity of phlD from 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas spp.
    Scientific Societies ; 2001
    In:  Phytopathology® Vol. 91, No. 1 ( 2001-01), p. 35-43
    Details
    In: Phytopathology®, Scientific Societies, Vol. 91, No. 1 ( 2001-01), p. 35-43
    Abstract: Fluorescent Pseudomonas spp. that produce 2,4-diacetylphloroglucinol (2,4-DAPG) have biocontrol activity against damping-off, root rot, and wilt diseases caused by soilborne fungal pathogens, and play a key role in the natural suppression of Gaeumannomyces graminis var. tritici, known as take-all decline. Diversity within phlD, an essential gene in the biosynthesis of 2,4-DAPG, was studied by restriction fragment length polymorphism (RFLP) analysis of 123 2,4-DAPG-producing isolates from six states in the United States and six other locations worldwide. Clusters defined by RFLP analysis of phlD correlated closely with clusters defined previously by BOX-polymerase chain reaction (PCR) genomic fingerprinting, indicating the usefulness of phlD as a marker of genetic diversity and population structure among 2,4-DAPG producers. Genotypes defined by RFLP analysis of phlD were conserved among isolates from the same site and cropping history. Random amplified polymorphic DNA analyses of genomic DNA revealed a higher degree of polymorphism than RFLP and BOX-PCR analyses. Genotypic diversity in a subset of 30 strains representing all the phlD RFLP groups did not correlate with production in vitro of monoacetylphloroglucinol, 2,4-DAPG, or total phloroglucinol compounds. Twenty-seven of the 30 representative strains lacked pyrrolnitrin and pyoluteorin biosynthetic genes as determined by the use of specific primers and probes.
    Type of Medium: Online Resource
    ISSN: 0031-949X , 1943-7684
    URL: Article
    DOI: 10.1094/PHYTO.2001.91.1.35
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2001
    detail.hit.zdb_id: 2037027-1
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Effect of Population Density of Pseudomonas fluorescens on Production of 2,4-Diacetylphloroglucinol in the Rhizosphere of Wheat
    Scientific Societies ; 1999
    In:  Phytopathology® Vol. 89, No. 6 ( 1999-06), p. 470-475
    Details
    In: Phytopathology®, Scientific Societies, Vol. 89, No. 6 ( 1999-06), p. 470-475
    Abstract: The role of antibiotics in biological control of soilborne pathogens, and more generally in microbial antagonism in natural disease-suppressive soils, often has been questioned because of the indirect nature of the supporting evidence. In this study, a protocol for high pressure liquid chromatography/mass spectrometry is described that allowed specific identification and quantitation of the antibiotic 2,4-diacetylphloroglucinol (Phl) produced by naturally occurring fluorescent Pseudomonas spp. on roots of wheat grown in a soil suppressive to take-all of wheat. These results provide, for the first time, biochemical support for the conclusion of previous work that Phl-producing fluorescent Pseudomonas spp. are key components of the natural biological control that operates in take-all—suppressive soils in Washington State. This study also demonstrates that the total amount of Phl produced on roots of wheat by P. fluorescens strain Q2-87, at densities ranging from approximately 10 5 to 10 7 CFU/g of root, is proportional to its rhizosphere population density and that Phl production per population unit is a constant (0.62 ng/10 5 CFU). Thus, Phl production in the rhizosphere of wheat is strongly related to the ability of the introduced strain to colonize the roots.
    Type of Medium: Online Resource
    ISSN: 0031-949X , 1943-7684
    URL: Article
    DOI: 10.1094/PHYTO.1999.89.6.470
    Language: English
    Publisher: Scientific Societies
    Publication Date: 1999
    detail.hit.zdb_id: 2037027-1
    SSG: 12
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