Abstract:[Background] In the context of sustainable agricultural development, complex microbial agents have emerged as a potent means for enhancing plant growth, attributed to the synergistic effects of diverse microorganisms. [Objective] To investigate the rhizosphere complex microbial agent of Dicranopteris dichotoma regarding the effects on the growth and rhizosphere microbial community structure of mung bean seedlings. [Methods] Four plant growth-promoting strains isolated from the rhizosphere soil of D.dichotoma were used to formulate two complex microbial agents: BBF and BFF. The agents were inoculated into the rhizosphere of mung bean seedlings, and the physiological parameters and soil physicochemical characteristics of the mung bean seedlings were evaluated after 36 days of cultivation. The community structure and diversity of rhizosphere microorganisms were assessed by 16S rRNA gene and ITS amplicon sequencing. [Results] BFF increased the plant height, aboveground fresh and dry weights, and underground dry weight of mung bean seedlings by 29.38%, 81.47%, 175.73%, and 936.49%, respectively. BBF increased the aboveground fresh weight and dry weight of mung bean seedlings by 92.64% and 179.67%, respectively. High-throughput sequencing results revealed that both BFF and BBF significantly boosted the bacterial diversity and richness, while reducing the fungal diversity. At the phylum level, the two agents increased the relative abundance of Myxococcota while decreasing that of Zygomycota. At the bacterial genus level, the two agents decreased the relative abundance of Rhodanobacter while increasing that of Mucilaginibacter and Bradyrhizobium; at the fungal genus level, the two agents increased the relative abundance of Cryptococcus while decreasing that of Mortierella and Gliocladiopsis. Functional prediction indicated that the application of complex microbial agents notably enhanced bacterial nitrogen fixation in the rhizosphere, increased the relative abundance of pathogenic-saprophytic-symbiotic fungi, and decreased the relative abundance of saprophytic and saprophytic-symbiotic fungi. [Conclusion] Inoculating complex microbial agents increases soil nutrients, regulates rhizosphere microbial community structure and diversity, boosts beneficial bacterial count, and suppresses pathogen presence, thus creating a favorable environment for the root growth and promoting the growth and development of mung bean seedlings. These findings offer new theoretical support for the growth of mung bean seedlings and establish a basis for applying complex microbial agents in agricultural production.
