Regulatory Mechanisms of Synthetic Microbial Communities on Rhizosphere Microecology to Alleviate Continuous Monoculture Obstacles of Medicinal Plants

Driven by industrial policies and market expansion, China has formed the world's largest medicinal plant cultivation industry. However, sustainable herbal production is seriously hindered by continuous monoculture obstacles (CMOs), which arise from prolonged single-species successive cultivation and manifest as comprehensive soil degradation featuring autotoxic allelochemical buildup, unbalanced rhizosphere microbiota, impaired soil physicochemical conditions, and frequent soil-borne pathogen outbreaks. Such adverse alterations lower soil enzyme activity, disrupt microbial community homeostasis, and severely impair both the yield and bioactive constituent quality of medicinal plants. Synthetic microbial communities (SynComs), experimentally assembled from defined microbial isolates via precise cultivation and controlled assembly, exhibit promising potential to regulate plant metabolism, optimize nutrient cycling and boost plant stress tolerance, and thus may serve as a feasible strategy to mitigate medicinal plant CMOs. This review took rhizosphere microecology as its core research perspective and summarized CMOs' status, SynComs' significance, construction methods, and their mechanisms in reshaping rhizosphere microecology-focusing on root exudates, nutrient cycling and microbiome dynamics. SynComs adjusted root exudates, participate in carbon/nitrogen/phosphorus cycling, enhance stress/pathogen resistance, and strengthen root immunity via signaling pathways (e.g. jasmonic acid). Existing experimental evidence indicated SynComs may partially repair plant-microbe communication networks impaired under continuous monoculture. Future research should prioritize innovative SynCom designs with keystone microbes, improved assembly techniques, and deeper rhizosphere mechanistic studies to advance sustainable medicinal plant production.