Differences in rhizosphere microbial community structure in oilseed rape with different degrees of clubroot severity

To examine how clubroot severity impacts oilseed rape rhizosphere microbial communities, this study analyzed rhizosphere soil samples from healthy, mildly infected, and severely infected plants. We assessed total microorganism content and conducted 16S rRNA and ITS region sequencing to explore microbial community structure and diversity, predict bacterial and fungal functions, and track changes in beneficial and pathogenic microbes. Results showed that clubroot severity affects rhizosphere microbial diversity and community structure. The richness of rhizosphere bacteria was ranked as follows: disease-free > mild > severe, while that of rhizosphere fungi was ranked as follows: mild > severe > disease-free. Proteobacteria, Bacteroidota, and Firmicutes were the dominant bacterial phyla, while Pseudomonas, Flavobacterium and Rhizobium were the dominant bacterial genera in the soil samples tested. The dominant fungal phyla in rhizosphere soil were Olpidiomycota, Ascomycota and Chytridiomycota, while the dominant fungal genera were Olpidium, Fusarium, and Plectosphaerella. The occurrence of clubroot increased bacterial functions such as Environmental_Information_Processing and Cellular_Processes in the rhizosphere of oilseed rape, and decreased functions such as Organismal_Systems, Genetic_Information_Processing and Metabolism. Clubroot also increased the abundance of Saprotroph-type fungi and decreased the abundance of fungal/animal parasite-type fungi in the rhizosphere. Furthermore, as clubroot severity increased, the abundance of beneficial microorganisms in the rhizosphere exhibited a decreasing trend, while that of pathogenic microorganisms showed an increasing trend. Our findings demonstrated that the structure, composition and diversity of rhizosphere microbial communities were closely related to the occurrence and severity of clubroot, thus providing an effective approach to synthesizing beneficial microorganisms, in order to control clubroot, alleviate soil degradation, and rebuild healthy soils.