Multi-trait Halotolerant Plant Growth-promoting Bacteria Mitigate Induced Salt Stress and Enhance Growth of Amaranthus Viridis

Purpose The constantly changing global environment causes abiotic stressors, which have a negative influence on plant development and output. Among abiotic pressures, soil salinity is a major impediment to meeting global food demands while also ensuring sustainable agriculture. To address this issue, the current study sought multi-functional microbial inoculants from challenging habitats that can work together to alleviate salt stress. Methods To pre-isolate plant growth-promoting bacteria (PGPB), samples were collected from the halotolerant plant Suaeda nudiflora found in saline desert soil. Isolates were screened for morphological, biochemical, and molecular characterization and in planta screening under greenhouse conditions. Results Endophytic Bacillus safensis (BS) and rhizospheric Bacillus haynesii (BH) strains showed significant plant growth-promoting properties under in vitro conditions and were further examined in a greenhouse for the growth promotion of the Amaranthus viridis plantlets under salinity (4 ds m(-1) and 6 ds m(-1)) conditions. Both strains were able to produce gibberellic acid, indole-3-acetic acid, hydrogen cyanide, ammonia, 1-amino cyclopropane-1-carboxylic acid deaminase, exopolysaccharides, protease, chitinase, amylase, cellulase, and solubilized minerals such as phosphorous, zinc, and potassium. Stain BS was able to produce siderophore, while strain BH was able to fix nitrogen and produce pectinase. Both strains were effective under abiotic stress conditions such as pH, temperature, salt, and drought. Conclusion The application of halotolerant multi-trait PGPB is a viable and environmentally beneficial strategy for improving salt tolerance in plants. Consortiums were found to be more effective than single-strain inoculation at promoting plant development in salinity, and they have the potential to be developed further as a unique bioformulation product.