Effet PGPR des souches de Pseudomonas fluorescens isolées de la rhizosphère du blé cultivé dans la région de Constantine

Abstract

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.