Effets des PGPR sur l’amélioration de la croissance végétale sous stress abiotique

Abstract

Abiotic stresses, whether single or combined, are a major obstacle to crop productivity, compromising plant growth and significantly reducing crop yields. The use of microbial technologies in agriculture is spreading very rapidly, with the identification of new bacterial strains effective in enhancing plant growth (PGPB, Plant Growth Promoting Bacteria). The aim of the present study was to identify multi-tolerant PGPB to mitigate the effects of abiotic stresses on the growth of durum wheat (Triticum durum L.). 24 bacterial strains from various ecosystems are being evaluated for their PGP traits and their ability to tolerate various stresses (drought, salinity, temperature, pH, heavy metals, pollutants, herbicides and fungicides). The most effective bacterial strains, Providencia vermicola ME1, Pantoea agglomerans Pa, Pseudomonas knackmussi MR6 and Bacillus sp. D13, are selected for water stress mitigation. These strains showed significant PGP activity under osmotic stress (0, 10, 20 and 30% PEG- 6000). They are then used to inoculate wheat under water stress at two growth stages. These osmotolerant PGPBs significantly improved seed germination parameters. The pot experiment was evaluated on wheat plants subjected to three irrigation regimes: well-watered (100% field capacity (FC)), moderate stress (50% FC) and severe stress (25% FC). Results showed that bacterial inoculation mitigated the adverse effects of drought and significantly improved morphological, physiological and biochemical parameters. The favorable adaptability of these bacteria under stress is attributed to the increase in root colonization capacity observed under the microscope on wheat plant roots after staining following triphenyl chloride (TTC) reduction. To prove the efficacy of these PGPB as inoculants under multiple abiotic stresses (salinity, drought, cadmium and phenanthrene), strain Pa was chosen for its multi- tolerance (MT-PGPB). The strain's performance can be seen in its PGP activities under singleor combined stresses. The effects of combined stresses on wheat growth resulted in a marked reduction in morphological parameters (plant size and biomass).