Fusarium enrichment alters the soil microbial community and network structure of Brassica crops

Soil-borne microbial diseases constitute a significant constraint on crop production, causing substantial annual economic losses estimated at 40%-60% in agricultural sectors. This study aimed to identify the principal plant pathogens causing diseases in Brassica crops in Ningxia, China, and the factors and mechanisms of infection. Employing ITS and 16S rRNA gene high-throughput sequencing, we investigated the soil microbial community associated with both healthy and diseased Brassica crops, as well as other main crops. We detected significant abundances of the soil-borne pathogenic fungi Fusarium and Olpidium, with Fusarium markedly enriched in diseased soils, suggesting its potential role in pathogenesis. Furthermore, the disease presence induced substantial disturbance in the soil fungal community, whereas the prokaryotic community structure remained relatively unaffected. Spatial and environmental factors exerted a more pronounced influence on fungal communities than on prokaryotic communities, with disease incidence attenuating the impact of environmental variables on fungal assemblages. Further analysis revealed that soil properties positively drove Fusarium abundance, and this proliferation synergized with soil factors to reduce fungal evenness. This evenness loss, coupled with the pathogen's direct effect, ultimately led to network simplification and a vulnerable "low evenness-high complexity" state. Network analyses confirmed this vulnerability, showing heightened complexity but diminished stability in fungal networks within diseased soils. Collectively, our findings provide a theoretical and technical framework for the rapid identification and effective management of pathogens affecting Brassica crops. KEY POINTS: Fusarium is significantly and highly enriched in diseased Brassica soil. Fungal community exhibits distinct patterns in diseased Brassica soil. Diseased soil exhibits more complex, less stable fungal networks.