Impact of Bio-inoculation with Halotolerant Rhizobacteria on Growth, Physiological, and Hormonal Responses of Durum Wheat Under Salt Stress

Soil salinity and water scarcity are major factors limiting plant productivity. Under these conditions, the use of plant growth-promoting rhizobacteria (PGPR) is a promising tool to mitigate the negative effects of stress in plants. Our study aims to determine the effect of two bacteria selected on the basis of their high halotolerance and ability to promote plant growth. Phylogenetic analysis and total 16S rDNA sequences showed that the first strain used (BSSM328) belongs to the genus Halomonas, and the second strain (BSSM27) belongs to the genus Kushneria. The effects of these two strains are evaluated by monitoring some growth (Shoot and Root length, Shoot and Root Dry Weight), physiological, biochemical, and hormonal (Abscisic acid, Jasmonic acid, Salicylic acid) parameters in the absence and presence of salt stress (100 and 200 mM NaCl). The results obtained showed that the growth of durum wheat was significantly stimulated by inoculation while salt induced an inhibitory effect proportional to the severity of salt stress. Both strains significantly reduced proline levels, relative electrolyte leakage, and abscissic and jasmonic acid content when exposed to salt stress. Salicylic acid content varied with NaCl concentration and strain used. In contrast, they significantly increased total chlorophyll content and decreased carotenoid content. The reduction in total antioxidant capacity and malondialdehyde levels under these conditions was not significant. Both strains used showed great potential to suppress the effects of salt stress on durum wheat growth, with a superior effect for strain BSSM27. Therefore, they could be used as bio-inoculants to improve wheat performance and productivity in arid and semi-arid regions.