Halotolerant Bacterial Inoculation Mitigates Salinity-Induced Morpho-Physiological Stress in Rhodes Grass (Chloris...

Salinity is a major constraint to pasture establishment and productivity, particularly in marginal soils. This study evaluated the effect of halophilic and halotolerant plant growth-promoting bacteria (PGPB) on germination and early vegetative growth of Rhodes grass (Chloris gayana cv. Reclaimer) under saline stress. Seven bacterial strains, previously isolated from hypersaline environments, were tested during germination of caryopses and spikelets at 0, 100, and 300 mM NaCl. The three most effective strains (Halomonas sp. 3R12, Pseudomonas sp. AN23, and Pseudarthrobacter sp. ER25) were further evaluated in a hydroponic system at 0 and 300 mM NaCl for morphological, biochemical, ionic, and photosynthetic parameters. Halomonas sp. 3R12 enhanced germination across all salinity levels, while Pseudomonas sp. AN23 and Pseudarthrobacter sp. ER25 showed seed-type-dependent effects. Under salt stress, bacterial inoculation increased plant height and root dry weight, reduced leaf Na⁺ accumulation, and improved K⁺/Na⁺ and Ca²⁺/Na⁺ ratios, indicating restricted Na⁺ translocation. Halomonas sp. 3R12 also promoted higher antioxidant activity and proline content, while Pseudarthrobacter sp. ER25 and Pseudomonas sp. AN23 improved the photosynthetic performance. These bacteria maintained the photosynthetic efficiency (Fv/Fm, Phi2) in plants under stress, in contrast to non-inoculated plants, which showed activation of regulated energy dissipation mechanisms and reduced electron flow. Overall, Halomonas sp. 3R12 and Pseudarthrobacter sp. ER25 were the most effective strains supporting their potential as bioinoculants for improving forage grass performance in salt-affected soils.