Fusarium cross-infection in medicinal herbs alters rhizosphere microbiomes and disrupts mycorrhizal functions under soil physicochemical imbalances

Background and Aims Fusarium root rot and wilt affect medicinal herbs in Gansu Province, China, despite extended crop rotations. This study investigated the cross-pathogenicity of Fusarium species isolated from Angelica sinensis (Danggui), Codonopsis pilosula (Dangshen), and Astragalus mongholicus (Huangqi). Methods Of 83 fungal isolates recovered, 69.8% were identified as Fusarium spp., through ITS, TEF1-α, and RPB2 sequencing, clustering into Fusarium oxysporum (FOSC, 36.2%), Fusarium solani (FSSC, 31%), and Fusarium tricinctum (FTSC, 22.4%) species complexes. Representative strains ( F. oxysporum DSH27, F. solani HQ123, F. tricinctum DG105) were tested for cross-pathogenicity in greenhouse and field trials. Rhizosphere microbial dynamics, including fungal and bacterial community diversity, functional guilds, and soil physicochemical properties, were analyzed. Results Fusarium strains exhibited varying aggressiveness, highest on original hosts, while cross-infective hosts showed less to moderate severity. Infections disrupted rhizosphere networks, increasing pathotrophic dominance over arbuscular mycorrhizal functions. Sequencing showed reduced fungal and bacterial operational taxonomic units (OTUs), with distinct clustering of infected vs. non-infected rhizospheres. Pathogenic fungal genera Fusarium positively correlated with disease incidence, while beneficial fungal genera Mortierella and bacterial genera RB41 showed negative correlations. Infected soils exhibited significant changes in total carbon, available phosphorus, manganese, and zinc, correlating with microbial dynamics and disease severity. Conclusion This study links Fusarium cross-infection with rhizosphere microbial network disruptions, including the loss of arbuscular mycorrhizal fungi (AMF) functions under altered soil physicochemical conditions in medicinal herbs. These findings uncover the systematic cross-pathogenicity of Fusarium species, highlighting the need for AMF-based strategies and integrated soil management to mitigate its impact.