Lactobacillus reuteri metabolites alleviate apple replant disease (ARD) by driving beneficial bacteria to reshape the core root microbiome.

Previous studies have shown that the bacterial fertilizer Lactobacillus reuteri (LBR) significantly alleviates apple replant disease (ARD), but the mechanism behind its effectiveness remains unclear. This study investigated the effects of key LBR metabolites on the rhizosphere microbial community. The biocontrol function of extracellular polysaccharides (EPS) was examined and shown to be further enhanced after optimizing the fermentation conditions. The optimized fermentation conditions were found to generate intermediates involved in various plant metabolic pathways, leading to plant growth promotion, increased abundance of beneficial bacteria like Bacillus and Pseudomonas in the rhizosphere soil, and decreased abundance of pathogenic fungi. Through the isolation and identification of rhizosphere microorganisms, a strain of Pseudomonas monteilii with chemotaxis to EPS was isolated, which had growth promotion ability and effectively improved plant resistance and relieves ARD. To further understand the mechanism underlying the inhibitory effect on soil pathogens of microbial aggregations and development in the rhizosphere driven by beneficial bacteria metabolites. These findings offer valuable technical insights for utilizing biocontrol bacteria metabolites in ARD management.