Crop rotation with marigold promotes soil bacterial structure to assist in mitigating clubroot incidence in Chinese cabbage

Clubroot caused by Plasmodiophora brassicae is an economically important soilborne disease of Chinese cabbage all over China. Integrated biological control through crop rotation is considered a good disease management approach to suppress the incidence of soilborne diseases. In this study, we evaluated the effect of a marigold plant (root exudates, crude extract, and powder) on the germination and death of resting spores of P. brassicae in in-vitro assays. Additionally, we also performed 16S high throughput sequencing to investigate the impact of Marigold-Chinese cabbage crop rotation on soil bacterial community composition to manage this devastating pathogen. This study revealed that the marigold root exudates, crude extract, and powder significantly promote the germination and death of P. brassicae resting spores. At field conditions, the Marigold-Chinese cabbage crop rotation with an empty period of at least 15 days enhances the germination of P. brassicae resting spores, shifts the rhizosphere bacterial community composition, and suppresses the incidence of clubroot by up to 63.35%. We conclude that crop rotation of Chinese cabbage with marigold can significantly reduce the incidence of clubroot disease in the next crop. To our knowledge, this is the first comprehensive study on the prevention and control of clubroot disease of Chinese cabbage through crop rotation with the marigold.