Alfalfa Rotation Enhances Soil Microbial Diversity and Reduces <i>Tilletia foetida</i> DNA Abundance in Common Bunt-Infected Wheat Fields

The pathogenic fungus Tilletia foetida causes common bunt in wheat, replacing grains with black spores and consequently reducing yield and quality. To assess the impact of crop rotation on soil health and pathogen dynamics, we investigated the effects of Medicago sativa L. (alfalfa) rotation on common bunt-infected wheat fields, compared with Avena sativa L. (oat) rotation. Soil eukaryotic communities were analyzed using Illumina MiSeq 18S rDNA sequencing. Additionally, soil physicochemical properties, enzyme activities (urease, phosphatase, peroxidase, and sucrase), and the abundance of T. foetida DNA were measured. Results showed that alfalfa/wheat rotation increased soil eukaryotic communities in the soil rhizosphere. The most abundant phyla were Mucoromycota, Mollusca, and Basidiomycota. While total phosphorus (TP), total nitrogen (TN), and pH remained largely unchanged, NO3--N, NH4+-N, and available potassium (AK) levels varied, correlating with changes in enzyme activities and soil eukaryotic communities composition. Compared with diseased wheat monoculture, alfalfa rotation was associated with significantly lower soil T. foetida DNA abundance and enhanced soil enzyme activity. These findings indicate that alfalfa rotation substantially improves the soil eukaryotic community, and plays a crucial role in reducing the T. foetida DNA abundance in soil.