Effect of mono- or bi-species Arbuscular mycorrhizal symbioses in improving the salt stress tolerance in Sorghum bicolor (L.) Moench.

Background and Aims: Salt stress is one of the most significant environmental constraints to agriculture, resulting in decreased crop productivity. The study aims to investigate the salt-stress alleviation effects of two potential Arbuscular Mycorrhizal Fungi (AMF), viz . Funneliformis mosseae and Rhizophagus intraradices , on the growth and metabolic changes of Sorghum plants. Methods A pot experiment was conducted under greenhouse conditions for 120 days in two different salt stress conditions (NaCl at 150 mM, EC 7.32 dS/m, and 300 mM, EC 12.03 dS/m) with/without AMF species, either alone or in combination. The AMF colonization and biochemical parameters were estimated at 30-day intervals. Results The total biomass, chlorophyll, carbohydrate, phosphate, nitrate, and proline contents increased in combined AMF-colonized plants exposed to 150 mM NaCl stress compared to the AMF-untreated control. In contrast, 300 mM salt stress significantly reduced AMF colonization and plant growth parameters. In 150 mM NaCl-stressed plants, the combined AMF-treated plants exhibited higher SOD, CAT, and APX activity compared to the AMF-untreated control plants, and lowered MDA and H ₂ O ₂ contents. The essential mineral contents were increased, while the uptake of Na+ ions was decreased. Conclusion The study concludes that dual-species AMF-treated plants (Fm + Ri) ameliorated salt stress more effectively by modulating ion uptake, enhancing stress defense enzymes, and minimizing redox factors, compared with salt-stressed AMF-untreated control plants and single-species AMF inoculations, resulting in a collective improvement in plant growth parameters. Thus, a consortium of AMF species ( R. intraradices and F. mosseae ) could be an efficient ameliorator of salt stress in sorghum cultivation.