Arbuscular mycorrhizal fungi reshape rhizosphere microbial communities to alleviate phosphorus deficiency in soda-saline soils

Abstract

Phosphorus availability is severely constrained in soda saline-alkali soils; yet the mechanisms by which arbuscular mycorrhizal (AM) fungi modulate rhizosphere microbial communities to alleviate the limitation are still unresolved. In the research, a microcosm experiment is conducted with metagenomic sequencing to investigate how inoculation with Rhizophagus intraradices influenced rhizosphere properties, phosphorus fractions, phosphatase activities, microbial community structure, P-cycling gene networks, and growth of Elaeagnus angustifolia under soda saline-alkali stress. The results demonstrated that AM inoculation was associated with enhanced plant growth and root development, ameliorated rhizosphere physicochemical conditions, elevated phosphatase activities, and enrichment of organic phosphorus-mineralizing bacteria, primarily Actinobacteria (Streptomyces) and Proteobacteria (Pseudoxanthomonas, Sphingomonas, Variovorax). Critically, the P-cycling gene network was reorganized, with hubs shifting from inorganic phosphorus transport genes toward organic phosphorus mineralization genes. Variance partitioning analysis further indicated that AM fungi independently contributed to variation in P-cycling functional genes, whereas their influence on soil phosphorus pools and phosphatase activity appeared to be largely indirect and associated with changes in soil chemical properties. Collectively, these findings support the hypothesis that AM fungi may promote phosphorus mobilization and transfer toward plants by restructuring microbial community composition and functional potential, providing a foundation for microbial management strategies in soda saline-alkali soils.