Fungicides reduce soil microbial diversity, network stability and complexity in wheat fields with different disease resistance

The decline in soil microbial diversity induced by fungicides presents a significant global environmental challenge, as highlighted by the United Nations Environment Program (UNEP), which emphasizes the serious threat posed to food production and human health by soil degradation. Despite this, there is a shortage of studies investigating the effects of fungicides on soil microbial functional diversity, assembly mechanisms, and network complexity in the proximal root zone of different wheat varieties. To bridge these knowledge gaps, we investigated the effects of a fungicide (tebuconazole) applied at a defined dose on wheat yield with different disease resistance and its proximal root zone soil bacterial and fungal communities using 16S rRNA gene sequencing. The results revealed that the application of fungicides increased the number of bacteria, decreased the number of fungi, and significantly reduced the diversity of fungi and bacteria (P < 0.05). Bacteria that function with the carbon and nitrogen cycles were also affected by fungicides, with a significant increase in abundance (P < 0.05). The complexity and stability of bacterial and fungal networks were significantly reduced, negative correlation increased, and microbial connectivity weakened under fungicide stress. The Mantel test analysis further indicated that changes in soil microbial structure were associated with changes in pH after fungicide application. In addition, fungicide application promoted deterministic processes in fungal and bacterial community assembly (null deviation value closer to 1), suggesting that enhanced soil selection and filtration processes altered soil microbial interactions. Overall, our study provides valuable insights into sustainable breeding strategies for disease-resistant wheat and sheds light on the potential adverse effects of fungicides on soil microbes and the environment.