Évaluation des propriétés bioactives et des capacités de tolérance environnementale des souches PGPR.

Abstract

This study evaluated the bioactive properties and salt stress tolerance of two rhizospheric bacterial strains, Bacillus pumilus BR7 and Pseudomonas cremoricolorata MR4, isolated from the rhizosphere of the halophyte Salsola tetrandra in the Bousaâda region. The two strains exhibit contrasting physiological and biochemical profiles, reflecting specific adaptations to their respective environments. Both produce indole-3-acetic acid (IAA), solubilize inorganic phosphate, and tolerate salt stress up to 1 M NaCl, confirming their potential as plant growthpromoting rhizobacteria (PGPR). However, only MR4 synthesizes siderophores, expresses tyrosinase, resists crystal violet, and exhibits marked production of HCN and urease, thereby strengthening its biocontrol potential. In contrast, BR7 stands out for its high growth rate under saline conditions, along with notable enzymatic activity (amylase, protease, and catalase), indicating a strong potential for enhancing soil fertility. Nevertheless, inoculation of durum wheat seeds (WAHA variety) with BR7 did not result in any significant improvement in germination rate or physiological growth parameters (root and shoot length, fresh and dry weight), under either normal or saline conditions. These findings suggest that the beneficial effects of this strain may manifest at later stages of plant development. Overall, the data highlight the importance of combined approaches and further research to optimize the use of these strains under diverse agronomic conditions, with a view toward promoting sustainable agricultural practices.