Liquid culture carbon, nitrogen and inorganic phosphate source regulate nematicidal activity by fluorescent pseudomonads in vitro

Siddiqui, I. A.; Shaukat, S. S.

doi:10.1111/j.1472-765x.2003.01472.x

Cited by 10 publications

(4 citation statements)

References 27 publications

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“…This resulted in poor growth and no production of DAPG, independent of the inorganic nitrogen source. These results are in contrast to results obtained by Siddiqui and Shaukat [ 26 ], who observed a nematicidal activity of filtrate from the DAPG-producing strain CHA0 when cultured on a medium lacking organic nitrogen. However, in their study it was not confirmed that the nematicidal activity was due to DAPG and other metabolites might have caused the biocontrol effect.…”

Section: Discussioncontrasting

confidence: 99%

Influence of Nitrogen Source on 2,4-diacetylphloroglucinol Production by the Biocontrol Strain Pf-5

Hultberg

Alsanius²

2008

TOMICROJ

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Abstract:The production of 2,4-diacetylphloroglucinol (DAPG) by the biocontrol agent Pseudomonas fluorescens Pf-5 was studied in nutrient-solution based media with varying nitrogen content. No production of DAPG was observed when organic nitrogen was omitted from the media, regardless of the inorganic nitrogen source used. Furthermore, a micromolar concentration range of organic nitrogen was insufficient to sustain production. When a millimolar concentration range of organic nitrogen was used, DAPG production was observed in the medium with ammonium as the inorganic nitrogen source. No production was observed in the treatments with ammonium and nitrate or nitrate only, despite growth of the bacterial strain being the same for all treatments. These results suggest that it is possible to manipulate the nutrient solution to increase the reliability and efficacy of biological control agents.

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Section: Discussioncontrasting

confidence: 99%

Influence of Nitrogen Source on 2,4-diacetylphloroglucinol Production by the Biocontrol Strain Pf-5

Hultberg

Alsanius²

2008

TOMICROJ

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“…2003) enhance the production of nematicidal agents in vitro and improve the biocontrol potential of P. fluorescens strain CHA0. Similarly, amino acids are also known to influence nematicidal activity by fluorescent pseudomonads in vitro (Siddiqui and Shaukat 2004b). Therefore, phenylalanine and asparagines were included in this experiment.…”

Section: The Effect Of a Methanol Fraction Of R Solani Culture Filtrmentioning

confidence: 99%

Phenylacetic acid-producing Rhizoctonia solani represses the biosynthesis of nematicidal compounds in vitro and influences biocontrol of Meloidogyne incognita in tomato by Pseudomonas fluorescens strain CHA0 and its GM derivatives

Siddiqui¹,

Shaukat²

2005

J Appl Microbiol

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I . A . S I D D I Q U I A N D S . S . S H A U K A T . 2004.Aims: The aim of the present investigation was to determine the influence of Rhizoctonia solani and its pathogenicity factor on the production of nematicidal agent(s) by Pseudomonas fluorescens strain CHA0 and its GM derivatives in vitro and nematode biocontrol potential by bacterial inoculants in tomato. Methods and Results: One (Rs7) of the nine R. solani isolates from infected tomato roots inhibited seedling emergence and caused root rot in tomato. Thin layer chromatography revealed that culture filtrates of two isolates (Rs3 and Rs7) produced brown spots at Rf-values closely similar to synthetic phenylacetic acid (PAA), a phytotoxic factor. Filtrates from isolate Rs7, amended with the growth medium of P. fluorescens, markedly repressed nematicidal activity and PhlAÔ-ÕLacZ reporter gene expression of the bacteria in vitro. On the contrary, isolate Rs4 enhanced nematicidal potential of a 2,4-diacetylphloroglucinol overproducing mutant, CHA0/pME3424, of P. fluorescens strain CHA0 in vitro. Therefore, R. solani isolates Rs4 and Rs7 were tested more rigorously for their potential to influence biocontrol effectiveness of the bacterial agents. Methanol extract of the culture filtrates of PAA-producing isolate Rs7 resulting from medium amended with phenylalanine enhanced fungal repression of the production of nematicidal agents by bacteria, while amendments with zinc or molybdenum eliminated such fungal repression, thereby restoring bacterial potential to cause nematode mortality in vitro. A pot experiment was carried out, 3-week-old tomato seedlings were infested with R. solani isolates Rs4 or Rs7 and/or inoculated with Meloidogyne incognita, the root-knot nematode. The infested soil was treated with aqueous cell suspensions (10 8 CFU) of P. fluorescens strain CHA0 or its GM derivatives or left untreated (as a control). Observations taken 45 days after nematode inoculation revealed that, irrespective of the bacterial treatments, galling intensity per gram of fresh tomato roots was markedly higher in soil amended with isolate Rs4 than in Rs7-amended soils. Soil amendments with R. solani and the bacterial antagonists resulted in substantial reductions of the number of galls per gram of root. These results are contradictory to those obtained under in vitro conditions where culture filtrates of PAA-positive Rs7 repressed the production of nematicidal compounds. Plants grown in Rs7-amended soils, with or without bacterial inoculants, had lesser shoot and root weights than plants grown in nonamended or Rs4-amended soils. Moreover, amendments with Rs7 substantially retarded root growth and produced necrotic lesions that reduced the number of entry sites for invasion and subsequent infection by nematodes. Populations of P. fluorescens in the tomato rhizosphere were markedly higher in Rs7-amended soils. Conclusions: PAA-producing virulent R. solani drastically affects the potential of P. fluorescens to cause death of M. incognita juveniles in vitro and infl...

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“…It has been reported in the last few decades that factors identified in vitro using liquid culture screening do indeed act as important virulence factors of phytopathogenic fungi and of microbial control agents such as entomopathogenic bacteria and entomopathogenic fungi (Bowen and Ensign, 1998;Fang et al, 2005;Siddiqui and Shaukat, 2004;St Leger et al, 1997;St Leger and Screen, 2001;St Leger and Wang, 2009). Based on this approach, most studies on the virulence factors of entomopathogenic fungi have been directed at elucidating the most relevant cuticledegrading enzymes (Griesch and Vilcinskas, 1998;Khachatourians, 1996;St Leger et al, 1996) because their overexpression in engineered strains results in more fungi that are more deadly towards insects (Fang et al, 2005;St Leger et al, 1996).…”

Section: Introductionmentioning

confidence: 98%

Insect-toxic secreted proteins and virulence of the entomopathogenic fungus Beauveria bassiana

Ortiz‐Urquiza

Riveiro-Miranda

Santiago‐Álvarez

et al. 2010

Journal of Invertebrate Pathology

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Liquid culture carbon, nitrogen and inorganic phosphate source regulate nematicidal activity by fluorescent pseudomonads in vitro

Cited by 10 publications

References 27 publications

Influence of Nitrogen Source on 2,4-diacetylphloroglucinol Production by the Biocontrol Strain Pf-5

Influence of Nitrogen Source on 2,4-diacetylphloroglucinol Production by the Biocontrol Strain Pf-5

Phenylacetic acid-producing Rhizoctonia solani represses the biosynthesis of nematicidal compounds in vitro and influences biocontrol of Meloidogyne incognita in tomato by Pseudomonas fluorescens strain CHA0 and its GM derivatives

Insect-toxic secreted proteins and virulence of the entomopathogenic fungus Beauveria bassiana

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