Objective Fusarium graminearum, is a pathogenic fungus that can cause a series of soil-borne diseases such as Fusarium Head Blight and Maize stalk rot, which seriously threatens food safety and human health. Taking advantage of microbial interactions to resist pathogenic fungus infection and reduce the abundance of pathogenic fungus in the soil is a new strategy for the prevention and control of soil-borne diseases. Among them, Pseudomonas has the great potential in inhibiting the growth and proliferation of pathogenic fungus. However, the impact of inoculating exogenous strains for soil microbial communities and its potential of cascading effects are unclear. The aims were to reveal the inhibitory effect of inoculating Pseudomonas on Fusarium graminearum in soil and its impact on indigenous microbial communities, and to ensure the optimal inoculation amount.

Method This study carried out indoor incubation experiment by inoculating different concentrations of Pseudomonas azotoformans (PA) and Pseudomonas mandelii (PM) up to 28 days. Using qPCR and amplified sequencing technology, regularly monitor the abundance of Fusarium graminearum in soil and the changes of indigenous microbial communities, and then to evaluate the potential application of specific Pseudomonas species in agricultural production.

Result The results showed that inoculating low concentrations of PM had better inhibitory effects on Fusarium graminearum in different sampling times (on the 7^th d and 28^th d), what inhibitory effects have been reached 22.73% and 43.56%. The analysis of soil microbial community composition and differential abundance of species showed that the inoculation of Pseudomonas could increase the relative abundances of Pseudoomonadaceae, Micrococcaceae and Intrasporangiaceae on the 7th day under the condition of pathogen infection. While the relative abundance of specific species could ben reduced, for example Sphingomonadaceae, Chloroflexaceae and Gaiellaceae. And on the 28^th day, the number of Rhizobiacea, Pseudoomonadaceae and Bdellovibrionaceae so on hadveincreased, while the relative abundances for Cladosporiaceae and Bacillaceae have been reduced. The enriched the specific species, such as Pseudoomonadaceae, Micrococcaceae and Rhizobiacea could promote soil organic matter turnover, improve the agricultural soil carbon sequestration and produce antibacterial substances to improve soil and plant health. The relative abundances of Acidobacteriota and Ascomycota were decreased, reflecting the eutrophication of soil microorganism after Pseudomonas had been inoculated. Therefore, inoculating low-concentration PM was the optimal concentration and species for reducing the abundance of Fusarium graminearum in soil.

Conclusion This study provides a green way the prevention and control of Fusarium graminearum, which offers a theoretical basis for field application of Pseudomonas spp., and the sustainable development of agriculture.