Ecological strategies determine continuous cropping susceptibility in Panax and Achyranthes

Medicinal plants frequently suffer from severe continuous cropping problems, yet it remains unclear whether divergent ecological strategies underlie species-specific susceptibility to this problem.

In this study, we investigated rhizosphere assembly patterns in three continuous cropping-sensitive Panax species (P. ginseng, P. quinquefolius, P. notoginseng) and the resilient species Achyranthes bidentata by analyzing paired cultivated and uncultivated soil samples from four major production regions in China. We measured soil physicochemical properties and enzyme activities and characterized bacterial (16S) and fungal (ITS) communities via amplicon sequencing. Plant-specific effects were quantified using Log₂ fold change relative to uncultivated controls.

The Panax species aggressively remodeled their rhizosphere, inducing significant acidification and ammonium accumulation (Log₂ FC up to 1.64 in P. notoginseng) while suppressing nitrification enzymes, and assembled fungal-dominated microbiomes enriched with pathogenic Nectriaceae, including Ilyonectria (LDA = 4.2) and Neocosmospora (LDA = 5.3). Their co-occurrence networks showed reduced stability, with negative correlations as low as 3.2%, and functional prediction indicated activated terpenoid metabolism (+74.8%). In contrast, A. bidentata maintained a neutral pH while specifically increasing available phosphorus (Log₂ FC = +1.74) and nitrate nitrogen (Log₂ FC = +0.74), and it enriched beneficial Actinobacteria by 15-85% and Hypocreales fungi. Its networks retained structural stability, with negative correlations of 12.7-18.6%. Plant species explained 60.5% of bacterial and 46.2% of fungal community variation, overwhelmingly exceeding the effect of soil compartment.

We conclude that Panax employs a resource-acquisitive strategy that assembles unstable, pathogen-prone microbiomes, whereas A. bidentata adopts a resource-conservative strategy that fosters resilient communities. This ecological framework offers a predictive basis for developing tailored microbiome management in medicinal plant cultivation.