Halotolerant Bacterial Diversity Associated with Suaeda fruticosa (L.) Forssk. Improved Growth of Maize under Salinity Stress

Abstract

Halotolerant bacterial strains associated with the rhizosphere and phytoplane of Suaeda fruticosa (L.) Forssk. growing in saline habitats were isolated to mitigate the salinity stress of Zea mays L. 16S rRNA gene sequencing confirmed the presence of strains that belong to Gracilibacillus, Staphylococcus, Virgibacillus, Salinicoccus, Bacillus, Zhihengliuella, Brevibacterium, Oceanobacillus, Exiguobacterium, Pseudomonas, Arthrobacter, and Halomonas genera. Strains were screened for auxin production, 1-aminocyclopropane-1-carboxylate (ACC)-deaminase, and biofilm formation. Bacterial auxin production ranged from 14 to 215 µg mL−1. Moreover, several bacterial isolates were also recorded as positive for ACC-deaminase activity, phosphate solubilization, and biofilm formation. In pot trials, bacterial strains significantly mitigated the salinity stress of Z. mays seedlings. For instance, at 200 and 400 mM NaCl, a significant increase of shoot and root length (up to onefold) was recorded for Staphylococcus jettensis F-11. At 200 mM, Zhihengliuella flava F-9 (45%) and Bacillus megaterium F-58 (42%) exhibited significant improvements for fresh weight. For dry weight, S. jettensis F-11 and S. arlettae F-71 recorded up to a threefold increase at 200 mM over the respective control. The results of this study suggest that natural plant settings of saline habitats are a good source for the isolation of beneficial salt-tolerant bacteria to grow crops under saline conditions.