FEMS Microbiology Ecology (2002) 39, 121-127

Jean-François Ghiglione, Agnès Richaume, Laurent Philippot and Robert Lensi (2002)
Relative involvement of nitrate and nitrite reduction in the competitiveness of Pseudomonas fluorescens in the rhizosphere of maize under non-limiting nitrate conditions
FEMS Microbiology Ecology 39 (2), 121-127
Abstract: Competition between different isogenic mutants of Pseudomonas fluorescens unable to carry out the first steps of the denitrification pathway was compared in soil micro-columns non-planted or planted with maize. A new isogenic mutant of P. fluorescens YT101 affected in both nitrate and nitrite respirations was constructed and used as a model of non-denitrifying strain (FM69MS strain). The outcome of the selection exerted by the plant after co-inoculation of FM69MS at the same ratio either with an isogenic denitrifier unable to reduce nitrate (Nar^- mutant) or with an isogenic NO₂^- accumulator (Nir^- mutant) was investigated in non-limiting NO₃^- conditions. Regardless of the inoculated mixture, both strains were able to grow in both rhizosphere and non-planted soil. The proportion of Nar^- or Nir^- strain in the Nar^-+FM69MS or Nir^-+FM69MS total introduced population remained stable in non-planted soil. In the rhizosphere, we observed a higher competitiveness of the Nir^- mutant compared with FM69MS, whereas the latter showed the same competitiveness as the Nar^- mutant. These results provide the first demonstration that NO₃^- reduction is the main nitrogen-dissimilating step controlling the competitiveness of P. fluorescens in the rhizosphere.
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Link to article at publishers website

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
environment/habitat manipulation
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
Pseudomonas fluorescens (antagonist)