Continuous cropping of soybean induced a more fluctuating fungal network and intensive pathogenic fungal interactions in a Mollisol of Northeast China

Abstract The effects of continuous cropping and crop rotation of soybean on soil fungal communities have been intensively studied, but we know little about the network structure and interactions among the fungal species impacted by these two cropping systems in the bulk and rhizosphere soils. In this study, through the Molecular Ecological Network Analysis Pipeline (MENAP), we constructed fungal ecological networks for bulk and rhizosphere soils under continuous cropping (CC) of soybean and cropping rotation (CR) with maize. The results showed that the network structures and characteristics were largely different between the two cropping systems in both the bulk and rhizosphere soils. Compared with the CR, the CC had simplified network structures in the bulk and rhizosphere soils. In the bulk soil, compared with the CR, CC formed a more stable network, which was resistant to environmental disturbance, but opposite trend was detected in the rhizosphere soil. More cooperative interactions among fungal species were found in CC than those in CR for both bulk and rhizosphere soils. Some functional fungi annotated to potentially pathogenic modes with highest node degree were found in CC network of rhizosphere soil, which had positive interactions with potentially pathogenic fungi and negative interactions with beneficial fungi. Taken together, continuous cropping of soybean weakened fungal network structure and strengthened the positive interactions among potentially pathogenic fungi in the rhizosphere soil.