Synergistic interaction between arbuscular mycorrhizal fungi and Falciphora oryzae enhances rhizosphere microbiota, plant growth, and nitrogen uptake in pepper

Arbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi (DSE) are pivotal root-associated microbes that promote plant growth and nutrient acquisition. Despite their ecological importance, the interactive mechanism underlying their relationship remains unclear. This study investigated the individual and combined effects of AMF ( Rhizophagus irregularis ) and Falciphora oryzae (FO, a DSE strain) on pepper ( Capsicum annuum ) growth, nutrient accumulation, and microbial communities across rhizosphere compartments. The results showed that co-inoculation of AMF and FO significantly increased the AMF root colonization rate while inhibiting FO colonization. All inoculation treatments significantly improved plant height, biomass, and nutrient uptake, with AMF + FO co-inoculation showing the most pronounced effects. While FO alone enriched soil nutrients, including nitrogen, phosphorus, and potassium, it was less efficient than AMF in facilitating plant nutrient uptake. Notably, the AMF + FO combination significantly increased nitrogen uptake in both roots and leaves compared to single inoculations. Microbiome analysis revealed a significant decline in microbial diversity and abundance closer to the internal root tissues. The AMF + FO combination specifically enriched microbial communities with nitrogen-fixing taxa such as Methyloversatilis and Paenibacillus , which correlated positively with soil and root nitrogen levels. In conclusion, the co-inoculation of AMF and FO significantly enhanced nitrogen uptake by improving soil nutrient status and enriching the microbial community, offering a novel strategy for improving crop nitrogen use efficiency. • Co-inoculation of AMF and Falciphora oryzae (FO) enhances pepper growth and N uptake. • AMF + FO reshapes rhizosphere microbiota and enriches beneficial N-fixing bacteria. • FO alone enriches soil nutrients but is less effective in plant N assimilation. • AMF mitigates FO-induced fungal shifts and favors potentially beneficial taxa. • AMF-FO synergy offers a sustainable strategy to enhance crop nutrient acquisition.