Growth improvement of Vicia faba planted in salt-affected soil by novel endophyte co-cultures

Salinity is a major problem that affects agricultural productivity. Plant growth-promoting bacteria (PGPB) may form a symbiotic relationship with their hosts to promote salt tolerance. Given the challenges of soil salinity in agriculture, this study explored the potential of halo-tolerant endophytic bacteria (halo-endophytes) as a bio-approach to promote plant growth under salinity stress. Five unique halo-endophyte strains (Providencia rettgeri DW3, Bacillus licheniformis DW4, Salinicoccus sesuvii DW5, Bacillus amyloliquefaciens DW6, and Paenalcaligenes suwonensis DW7), were used for the first time as bacteria promoting the growth of Vicia faba and soil fertility as well. Various bacterial combinations were investigated in a controlled greenhouse experiment. The unique combination of the five strains proved the most effective in alleviating the salinity’s harm to plant growth (growth percentages, photosynthetic rate, vegetative growth traits, and nutrient content) as well as proline content, which enhanced plant tolerance to salinity. Chemical and biological health features of the soil, measured by nutrient availability, microbial diversity and enzyme activity, improved by 110%, 753%, and 262%, respectively. This study demonstrates the effectiveness of co-inoculation with a bacterial mixture (P. rettgeri DW3 + B. licheniformis DW4 + S. sesuvii DW5 + B. amyloliquefaciens DW6 + P. suwonensis DW7) as a novel and innovative bio-based approach to sustainable agriculture in saline environments.