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

Hultberg M,Alsanius B

doi:10.2174/1874285800802010074

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.

Highlights

IntroductionIndigenous in the rhizosphere, produce and excrete secondary metabolites that are inhibitory to plant pathogens [1]
Some groups of pseudomonads, indigenous in the rhizosphere, produce and excrete secondary metabolites that are inhibitory to plant pathogens [1]
In medium A amended with only inorganic nitrogen sources, nitrate and ammonium nitrate (A1), nitrate only (A2) and ammonium only (A3), no production of DAPG was observed (Table 1)

Summary

Introduction

Indigenous in the rhizosphere, produce and excrete secondary metabolites that are inhibitory to plant pathogens [1]. They offer a sustainable alternative to pesticides and can provide disease control when the use of pesticides is legally restricted. Among the metabolites produced by Pseudomonas spp., the compound 2,4-diacetylphloroglucinol (DAPG) has been intensively studied due to its broad spectrum activity towards the commercially important plant pathogens Gaeumannomyces graminis var. The complex in situ condition in the natural rhizosphere influences survival, growth and production of secondary metabolites by the biocontrol strains. With respect to DAPG production, mineral and carbon sources as well as metabolites released by indigenous microflora and plants have been identified as being critical factors [12, 14,15,16]

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Conclusion