Plant-microbiome interactions suppress Fusarium wilt by enriching beneficial Aspergillus in the tobacco rhizosphere

Tobacco (Nicotiana tabacum) is a globally significant economic crop with a production that is severely threatened by soil-borne fungal pathogens, particularly Fusarium spp. Native rhizosphere microbial communities, especially those of root-associated fungi, have been suggested as sustainable solutions for disease suppression. However, the compositional differences in root-associated fungal communities between healthy and diseased tobacco plants remain poorly characterized. In this study, we investigated the root-associated fungal communities in healthy versus Fusarium-infected tobacco plants across three geographically distinct fields in Sichuan Province, China, to identify key microbial taxa involved in disease suppression. High-throughput sequencing revealed distinct fungal community compositions among the sites. The healthy rhizospheres were enriched with beneficial taxa, among which Aspergillus OTU2223 was the most dominant and potentially crucial for disease suppression. In contrast, diseased soils were dominated by pathogenic Fusarium taxa, with Fusarium solani being the most prevalent pathogen. Network analysis revealed that, compared with diseased soils, healthy rhizospheres maintained a greater number of nodes (306 vs. 282) and higher modularity (0.46 vs. 0.31) microbial interactions. We isolated and characterized Aspergillus strain A74, which demonstrated strong antagonistic activity against F. solani f. sp. nicotianae both in vitro and in greenhouse trials, thereby reducing the incidence of Fusarium wilt disease in greenhouse trials. The application of strain A74 maintained the growth parameters (including height, stem diameter, and chlorophyll content) of pathogen-inoculated plants at levels comparable to healthy plants. In summary, our study demonstrated that healthy tobacco plants assemble distinct root-associated fungal communities characterized by beneficial Aspergillus taxa that exhibit exceptional potential as biocontrol agents. These findings provide a theoretical foundation and practical support for the development of Aspergillus-based green biocontrol strategies, highlighting their potential as an environmentally friendly and sustainable approach to disease management in tobacco production.