Effects of Glomus intraradices Inoculation on Growth, Nutrient Uptake, and Rhizosphere–Endophytic Microenvironment of Sweet Potato Seedlings

Arbuscular mycorrhizal fungi (AMF) can improve plant performance, but how they coordinately influence root metabolism and associated bacterial communities in sweet potato remains unclear. Here, a pot experiment was conducted to investigate the effects of Glomus intraradices inoculation on sweet potato seedlings by integrating analyses of rhizosphere soil properties, plant growth and nutrient uptake, root metabolomics, and rhizosphere and endophytic bacterial communities using 16S rRNA gene sequencing with FAPROTAX-based functional prediction. AMF inoculation significantly increased whole-plant fresh and dry biomass, potassium concentration and accumulation, and the accumulation of starch and water-soluble carbohydrates, while no significant effects were observed on dry matter rate or plant nitrogen and phosphorus concentration. In the rhizosphere, AMF reduced soil electrical conductivity and increased organic matter content without significantly affecting pH, alkali-hydrolyzable nitrogen, available phosphorus, or available potassium. Root metabolomic profiling identified 289 differential metabolites, with enrichment of phenylpropanoid biosynthesis, glycerophospholipid metabolism, porphyrin metabolism, and nucleotide metabolism, together with broad up-regulation of lipid-related metabolites. Bacterial communities showed strong compartment specificity, with the root endosphere displaying lower alpha diversity than the rhizosphere. Higher rhizosphere bacterial Shannon diversity was observed in the AMF treatment, together with compartment-dependent shifts in bacterial community composition; enrichment of endophytic taxa such as Devosia and Niastella was detected following AMF inoculation. Functional prediction further suggested niche differentiation between rhizosphere and endophytic bacteria, together with AMF-associated shifts in carbon- and nitrogen-related functions. Overall, these results suggest that G. intraradices inoculation is associated with enhanced sweet potato growth and enhanced potassium and carbohydrate accumulation in association with coordinated changes in rhizosphere conditions, root metabolism, and bacterial community assembly.