Co-inoculation of a halotolerant Bacillus strain and arbuscular mycorrhizal fungi for improving plant growth in saline soils

Soil salinisation is a major factor limiting plant growth and land utilisation in arid and semiarid regions. This study focused on the native halophyte Suaeda salsa in western Inner Mongolia to explore halophyte-associated microbial resources with plant growth-promoting potential under saline conditions. A total of 30 salt-tolerant bacteria strains were isolated from its rhizosphere. Among them, Bacillus infantis strain 29 tolerated up to 10% NaCl (w/v) and exhibited multiple plant-growth-promoting traits, including highly active 1-aminocyclopropane-1-carboxylate (ACC) deaminase, indole-3-acetic acid (IAA) production, phosphorus solubilisation, potassium mobilisation and diazotrophic potential as indicated by growth on nitrogen-free medium. Under pot conditions, inoculation with strain 29, particularly in combination with arbuscular mycorrhizal fungi (AMF), promoted plant growth under saline stress. In Suaeda salsa, the combined treatment significantly increased fresh weight and root length relative to the control, and positive growth responses were also observed in Zea mays and Medicago sativa. This study proposes an effective "halophyte-PGPR-AMF" synergistic strategy and provides a potential biological approach and microbial resource reference for improving plant growth and crop performance in salt-affected soils of western Inner Mongolia and other arid and semiarid regions with similar environmental conditions.