Manipulation of microbial community in the rhizosphere alleviates the replanting issues in Panax ginseng

The replanting ginseng (Panax ginseng C. A. Meyer) in soil where ginseng has previously been grown usually fails due to issues associated with continuous cropping. Successful replanting requires a rotation cycle of more than 30 years. Crop failure at replant sites has been attributed to the accumulation of toxic substances in soil and changes in the rhizosphere microbiome. Soil acidification, toxic compound accumulation, and decreased bacterial diversity were detected in soils during ginseng cropping. The accumulation of toxic diisobutyl phthalate (DiBP) is negatively related to the abundance of Arthrobacter, Burkholderia, Rhodanobacter, and Sphingobacterium. A total of 153 strains were isolated from the rhizosphere soil of ginseng seedlings and identified as DiBP-degrading bacteria. Among these strains, Sphingobacterium sp. PG-1 degraded more than 90% of DiBP within 72 h. The abundance of PG-1 decreased by 79.9% in soils that were cropped with ginseng for three years. DiBP content decreased by 39.2%, and the ginseng death rate was decreased by 40.1% after replanting ginseng in soils inoculated with PG-1. Results revealed that the reduced abundance of DiBP-degrading microbes resulted in the accumulation of toxic compounds that disrupted the microbial ecology. This study provides insights into the integrated mechanism underlying replanting problems in terms of the chemical, biological, and genetic make-up of ginseng. Manipulating soil microbial communities is an effective strategy to alleviate ginseng replanting problems and increase crop productivity.