Impact of mycorrhizal inoculation on the fungal root and rhizosphere communities, growth and salinity tolerance of Alnus glutionosa Gaertn. seedlings

Abstract Background and Aims Alnus glutinosa L. Geartn. is a valuable forest tree species capable of thriving in saline soils, making it suitable for afforestation in moist, saline areas which are expanding under the influence of climate change. Its high salinity tolerance may stem from its ability to form dual mycorrhizal symbioses with arbuscular (AM) and ectomycorrhizal (EM) fungi in a single root system. Since seedlings in forest nurseries can be inoculated with mycorrhizal fungi prior to planting, this study aimed to determine which inoculation provides the best protection against salinity. Methods In an 11-month pot experiment, six-month-old A. glutinosa seedlings were inoculated with either AM fungi alone or a combination of AM + EM fungi under short-term (ST) and long-term (LT) salinity conditions. Results Both treatments increased plant growth under ST salinity, whereas AM was more effective under LT salinity. Mycorrhization contributes to maintaining the water content, proline accumulation, and lipid peroxidation in leaves. Both inocula reduced the sodium bioconcentration in leaves and roots, with AM + EM being more effective under ST salinity. Inoculation significantly influenced fungal beta diversity in roots and soil, particularly under ST salinity, whereas fungal alpha diversity remained unchanged or increased under LT conditions. It also increased the abundance of specific fungal genera in the endosphere and rhizosphere. Conclusion These findings highlight the potential of mycorrhizal inoculation to enhance A. glutinosa resilience in saline environments and support sustainable ecosystem restoration amid climate change.