Halomonas sp. for sustainable agriculture: a potential halo-bio-fertilizer for tomato plants with bio-control activity against Fusarium wilt under saline environments.

Halophilic bacteria are remarkable microorganisms that excel in hypersaline environments. Their significant potential in various fields, such as industry and agriculture, positions them as vital players in advancing our technological and ecological efforts. In this study, three bacterial strains were successfully isolated (QSLA1, QSLA2, and QSLA3) from solar saltern ponds using nutrient agar (NA) culture medium derived from pond water. Morphological and physiological characterization revealed that these isolates are rod-shaped, gram-negative, catalase-positive, and motile. Notably, QSLA1 and QSLA2 do not form spores, while QSLA3 is identified as a spore-forming bacterium. The halo tolerance assay demonstrated that QSLA1 and QSLA2 are extremely halophilic, whereas QSLA3 is classified as moderately halophilic. Through 16S rRNA sequence analysis, it was determined that QSLA1 shares 91.26% similarity with Halomonas sp. RS-17, while QSLA2 exhibits 96.6% similarity with Halomonas sp. strain LR2-3. QSLA3 shows even greater similarity at 97.33% to Halomonas sp. GQ30. All isolates are capable of producing indole-3-acetic acid (IAA), but only QSLA2 has the ability to fix atmospheric nitrogen and solubilize insoluble phosphate. Additionally, QSLA1 demonstrates antifungal activity against Fusarium oxysporium f.sp. lycopersici in vitro under saline environment. Given these promising traits, we explored the potential of QSLA1 as a bio-control agent under greenhouse conditions at 1.5% salinity.