Selection of a Bacterial Conditioner to Improve Wheat Production Under Salinity Stress

This study investigated the isolation and formulation of a bacterial conditioner as a biostimulant for <i>Triticum durum</i> (durum wheat) under salinity stress. An Algerian alkaline-saline soil was sampled, characterized for its physical and chemical characteristics and its culturable and total microbial community (16S rRNA gene metabarcoding). Three bacterial strains showing high 16S rRNA gene similarity to <i>Pseudomonas putida</i>, <i>Bacillus proteolyticus</i>, and <i>Niallia nealsonii</i> were selected for their plant growth-promoting (PGP) traits under different salinity levels, including phosphate solubilisation (194 µg mL^-1), hormone production (e.g., gibberellin up to 56 µg mL^-1), and good levels of hydrocyanic acid, ammonia, and siderophores. <i>N. nealsonii</i> maintained high indole production under saline conditions, while <i>B. proteolyticus</i> displayed enhanced indole synthesis at higher salt concentrations. Siderophore production remained stable for <i>P. putida</i> and <i>N. nealsonii</i>, whereas for <i>B. proteolyticus</i> a complete inhibition was registered in the presence of salt stress. The consortium density and application were tested under controlled conditions using <i>Medicago sativa</i> as a model plant. The effective biostimulant formulation was tested on <i>Triticum durum</i> under greenhouse experiments. Bacterial inoculation significantly improved plant growth in the presence of salt stress. Root length increased by 91% at 250 mM NaCl. Shoot length was enhanced by 112% at 500 mM NaCl. Total chlorophyll content increased by 208% at 250 mM NaCl. The chlorophyll a/b ratio increased by 117% at 500 mM. Also, reduced amounts of plant extracts were necessary to scavenge 50% of radicals (-22% at 250 mM compared to the 0 mM control). Proline content increased by 20% at both 250 mM and 500 mM NaCl. These results demonstrate the potential of beneficial bacteria as biostimulants to mitigate salt stress and enhance plant yield in saline soils.