Transcriptomic analysis of biological control of rust rot in Panax ginseng and the role of WRKY72B in enhancing pathogen resistance

Panax ginseng is a highly valued medicinal and economic crop in China. Rust rot, a major soilborne disease of ginseng, severely compromises its yield and quality, thereby constrains the sustainable development of the ginseng industry. Biological control is an effective strategy for preventing rust rot. Currently, numerous studies have focused on screening biocontrol strains and evaluating their antibacterial effects; however, research on the underlying molecular mechanisms of biological control remains limited. Therefore, in this study, the ginseng endophytic strains X14 and X19, as well as the chemical agent hymexazol, were applied to rust rot-infected ginseng, and the molecular regulatory network underlying biological control was elucidated using integrated transcriptomic and molecular approaches. The results showed that X14, X19, the combination treatment (X14 + X19), and hymexazol significantly increased cellulase and ascorbate peroxidase activities in ginseng roots but decreased proline content relative to the infected control. Transcriptome analysis showed that X14 upregulated the expression of genes associated with jasmonic acid (JA) and brassinosteroid (BR) metabolic pathways in rust rot-infected ginseng; strain X19 increased the expression of genes in the JA, BR, and ethylene (ETH) metabolic pathways; and the X14 + X19 combination upregulated only JA metabolic pathway-related genes. Meanwhile, the key differentially expressed gene PgWRKY72B was selected, and genetic transformation was performed in ginseng ARs. The overexpression lines exhibited greater resistance to rust rot than the wild type. This study elucidates the mechanism by which endophytes enhance ginseng resistance to rust rot through multiple hormone signaling pathways, thereby providing new insights for breeding rust rot-resistant ginseng varieties.