Wheat yellow mosaic enhances bacterial deterministic processes in a plant-soil system.

Understanding the mechanisms that govern microbial community assembly across soil-plant continuum is crucial for predicting the response of ecosystems to environmental changes. However, the impact of the health status of plant on microbial assembly across this continuum still remain poorly understood. Here, we investigated how wheat yellow mosaic (WYM), caused by the wheat mosaic virus transmitted by Polymyxa graminis, affected microbial assembly across soil (bulk soil, rhizosphere soil), and plant (roots and leaves) continuum in a winter wheat (Triticum aestivum L.) system in northern China, using null model analysis. The results showed that deterministic processes dominated the bacterial community assembly, whereas stochastic processes were primarily responsible for the assembly of the fungal communities. With increasing levels of WYM, deterministic processes were greatly enhanced for bacterial community assembly, accompanied by a decrease in community niche breadth. Intensified competition between bacteria and fungi and increased soil total nitrogen (TN) and soil organic carbon (SOC) contents were mainly responsible for the enhanced deterministic processes for bacterial community assembly. Random forest modeling indicated a strong potential of rhizosphere bacterial community assembly for predicting the pathological conditions of wheat. Structural equation modeling showed that disease level was positively correlated with SOC and TN contents, competitions between bacteria and fungi, and the contribution of variable selection processes to the bacterial community assembly in the wheat rhizosphere. Our study revealed the ecological mechanisms underlying the associations between microbial communities and soil-borne disease, and highlighted the significance of microbial community assembly for maintaining soil and plant health.