Impacts of continuous potato cropping on soil microbial assembly processes and spread of potato common scab

Abstract

Continuous cropping is a widely adopted cultivation system in intensive agriculture that can lead to a range of soil issues, ultimately affecting aboveground crops growth. However, the assembly process of soil microbial communities and the changes in pathogenic microorganisms under different years of continuous cropping remain unclear. The present study focused on the soil microbial community structure in potato geocaulosphere soil and potato common scab (CS) caused by pathogenic Streptomyces spp. We conducted pot experiment using five different continuous potato cropping soils and five alternative cropping soils (rotation potato cropping and non-potato monocropping). We used qPCR to detect pathogenic gene associated with CS and high-throughput sequencing to assess the microbial community composition. The results indicated that the microbial community structure in geocaulosphere is primarily influenced by the cropping history. Continuous cropping soils exhibited significantly increased bacterial richness and diversity compared to alternative cropping soils, with a distinct difference in microbial community composition. Moreover, null models revealed that deterministic processes driven by homogeneous selection predominated in shaping the assembly of microbial communities in continuous cropping soils. Short-term continuous cropping drove the assembly of soil bacterial communities towards deterministic processes through homogeneous selection, whereas with prolonged continuous cropping, the influence of homogeneous selection gradually diminished. The co-occurrence network of bacteria and fungi under continuous cropping exhibited characteristics of low average degree, high modularity, and high stability. Furthermore, continuous cropping increased the independence of fungal modules. The severity of CS and the presence of a pathogen-containing network module increased with the number of continuous cropping years, and the pathogen-containing network module demonstrated a significant positive correlation with CS. Collectively, our findings provide novel insights into the limitations of continuous agricultural cropping systems.