Improvement of barley seed performance and seedling growth by plant-growth-promoting bacteria

Biostimulants are widely acknowledged as an effective method to alleviate drought-induced stress in various plant species, particularly during the crucial germination stage. The goal of this study was to investigate how plant growth-promoting bacteria (Azospirillum lipoferum and Azotobacter chroococcum) affect specific biochemical characteristics of barley under different levels of drought stress (0, −6, and −12 bar). The study employed a factorial design with three replications using a randomized complete block design. Our results show that the interaction effect of inoculation treatments and stress levels on emergence percentage, mean emergence time, seedling dry weight, and ascorbate peroxidase (APX) activity level is significant at a 1% probability level. Additionally, the interaction effect on the emergence index, proline content, and catalase (CAT) activity level is substantial at a 5% probability level. There are highest emergence percentage (89.33%), emergence index (4.08), and seedling dry weight (0.923 g) and the lowest emergence rate (6.47 days), proline content (0.153 mg/g fresh leaf tissue), and CAT activity (29 mg/g fresh leaf tissue) in Azospirillum-inoculated seeds. The highest APX activity (19.30 mg/g fresh leaf tissue) was obtained under non-stress conditions. Overall, inoculation with Azospirillum bacteria has an influential role in modulating the destructive effects of drought stress on the evaluated traits.