Résumé:
Fluorescent pseudomonas can suppress various soilborne diseases, and their efficacy
related both; to their antagonistic activities and rhizosphere competitiveness. This study was
designed to isolate antagonistic Pseudomonas fluorescens from Wheat rhizosphere and evaluate
their Plant promoting traits. Fifty-five antagonistic strains were isolated from wheat soil,
cultivated in Constantine region (Algeria), characterized morphologically, biochemically and
molecularly, and screened for their Plant growth promoting traits. These PGP traits were
analyzed by phosphate solubilization, indol acetic acid (IAA), the production of siderophore,
ammonia, hydrogen cyanide (HCN), and the production of enzyme involved in the suppression
of the pathogen like cellulase, pectinase, chitinase, and protease. At the end, the biocontrol
capacity of these strains and growth promotion potential against two species of Fusarium: F.
culmorum and F. pseudograminearum were evaluated in planta. All the isolates showing a
biochemical and morphological of Pseudomonas fluorescens. Under in-vitro conditions, all
isolates produced cellulase and pectinase, 90.9% produced siderophore; hydroxamates type,
96.43% produced IAA. A 96.36% of isolates produced a clear zone around the colony,
exhibiting different sorts of phosphate solubilizing index (PSI) and 76.36% solubilized the
phosphate in liquid medium, 51.78% produced protease, 48.21% produced lipase, 16.36%
produced chitinase, and only 10.9% produced HCN. The selected strains inhibited Fusarium sp
growth and stimulated wheat growth with various extraction of enzymes when tested in pot
experiments. Nine bacterial strains, which showed a maximum plant growth promoting traits
using the molecular identification (16S rDNA gene sequence), were identified as Pseudomonas
fluorescens. This study concludes that strains ofPseudomonas fluorescens, isolated from wheat
rhizospheric soil from the region of Constantine (Algeria), showed variation in their plant
promoting characteristics production that can contribute to the ability of these isolates to
suppress fungal diseases. Based on the positive results of the antagonistic effect of selected
strains, it is interesting to use the PGPR Pseudomonas fluorescens as inoculants biofertilizers
to replace chemical fertilizers and pesticides for Wheat.
