Impact of 2,4-Diacetylphloroglucinol-Producing Biocontrol Strain Pseudomonas fluorescens F113 on Intraspecific Diversity of Resident Culturable Fluorescent Pseudomonads Associated with the Roots of Field-Grown Sugar Beet Seedlings

Abstract

The impact of the 2,4-diacetylphloroglucinol-producing biocontrol agent Pseudomonas fluorescens F113Rif on the diversity of the resident community of culturable fluorescent pseudomonads associated with the roots of field-grown sugar beet seedlings was evaluated. At 19 days after sowing, the seed inoculant F113Rif had replaced some of the resident culturable fluorescent pseudomonads at the rhizoplane but had no effect on the number of these bacteria in the rhizosphere. A total of 498 isolates of resident fluorescent pseudomonads were obtained and characterized by molecular means at the level of broad phylogenetic groups (by amplified ribosomal DNA restriction analysis) and at the strain level (with random amplified polymorphic DNA markers) as well as phenotypically (55 physiological tests). The introduced pseudomonad induced a major shift in the composition of the resident culturable fluorescent Pseudomonas community, as the percentage of rhizoplane isolates capable of growing on three carbon substrates (erythritol, adonitol, and L-tryptophan) not assimilated by the inoculant was increased from less than 10% to more than 40%. However, the pseudomonads selected did not display enhanced resistance to 2,4-diacetylphloroglucinol. The shift in the resident populations, which was spatially limited to the surface of the root (i.e., the rhizoplane), took place without affecting the relative proportions of phylogenetic groups or the high level of strain diversity of the resident culturable fluorescent Pseudomonas community. These results suggest that the root-associated Pseudomonas community of sugar beet seedlings is resilient to the perturbation that may be caused by a taxonomically related inoculant.

Fluorescent Pseudomonads associated with the rhizosphere of crops: an overview

“…Guimarães et al (47,48) and Araújo et al (4,5,6) observed that a strain of P. fluorescens and its OGM were able to survival and/or colonize bulk soil and rhizosphere of maize. Moënne-Loccoz et al (100) results suggested that the root-associated Pseudomonas community of sugar beet seedlings was resilient to the impact that may be caused by a taxonomically related inoculant. Nevertheless, the response of introduction of microorganisms will vary due to a plethora of factors that should be checked before considering their use as a BCA.…”

Applicability of the 16S–23S rDNA internal spacer for PCR detection of the phytostimulatory PGPR inoculant Azospirillum lipoferum CRT1 in field soil

“…This marker gene strategy presents other disadvantages as (i) the exogenous genes can represent a metabolic burden and may affect ecological fitness and/or phytostimulatory properties and (ii) cell enumeration following selective plating or microscopic observations is cumbersome and (with selective plating) does not enable monitoring of viable nonculturable cells. The second strategy, which is based on the use of spontaneous antibiotic‐resistant mutants (Moënne‐Loccoz et al. 2001; Mascher et al.…”

“…This would be of particular interest in the case of PGPR inoculants, where strain monitoring after large‐scale environmental release is an important issue, because these bacteria interact in various ways with different microbial components of the soil/plant microbiota (Kabir et al. 1996; Moënne‐Loccoz et al. 2001; Viebahn et al.…”

Molecular and phenotypic characterization of potential plant growth-promoting Pseudomonas from rice and maize rhizospheres

“…They have been studied intensively because of their ability to promote plant growth, either by directly stimulating the plant or by suppressing root pathogens. Moënne-Loccoz et al (2001) studied the culturable fluorescent pseudomonad community associated with the roots of field-grown sugarbeet seedlings using ARDRA, which suggested that the root-associated Pseudomonas community was flexible to the change that may be caused by adding a similar inoculant. Bakker et al (2002) further confirmed this using ARDRA by showing effects of biocontrol agents on the entire bacterial community in the rhizosphere of wheat.…”