Synergistic effects of native arbuscular mycorrhizal fungi and phosphorus-solubilising bacteria on alfalfa growth in semi-arid saline soils

Since phosphorus (P) availability is critical to plant productivity and crop performance, there is a growing focus on eco-friendly strategies to enhance its uptake. One of the most sustainable agricultural approach is the use of phosphorus-solubilising microorganisms. The present study aims to compare the inoculation of the forage legume Medicago sativa with rhizospheric microorganisms: a consortium of native arbuscular mycorrhizal fungi (AMF), native Phosphorus Solubilising Bacteria (PSB) (Pseudomonas luteola), and their co-inoculation under steppe saline soil conditions, using a factorial design combining microbial inoculation treatments and P fertilisation. Results showed that co-inoculation increased shoot biomass by 17 and 14% compared with AMF alone and PSB alone, respectively. Similarly, the total mycorrhizal rate increased by 17 and 23%, shoot P concentrations by 13 and 20%, and total protein content by 23 and 80%, respectively compared to AMF alone and PSB alone. A significant interaction between P supply and co-inoculation was observed, indicating that the synergistic effect depends on P availability. The efficiency of the co-inoculation can be attributed to the combined function of native AMF and P. luteola, which enhanced P solubilisation by 16% and its uptake by the host plant (+ 33 and + 17% compared with AMF alone and PSB alone). This interaction also improved protein content (+ 28%) and reinforced plant responses to saline stress (+ 70%). These findings highlight the strong potential of native AMF–PSB co-inoculation as a sustainable biofertilisation strategy to improve legume productivity and optimize P dynamics in semi-arid saline Algerian soils.