Radix pseudostellariae, belonging to the Caryophyllaceaeis family, is one of the most common and highly demanded Chinese medicines, which contains polysaccharides, ginseng saponins, flavonoids, cyclic peptides, amino acids and trace elements. However, consecutively monocultured R. pseudostellariae are prone to severe diseases, which may result in reduced biomass, especially of tuberous products. This phenomenon is known as replanting disease or soil sickness. More than 70 % of medicinal plants, especially tuberous root medicinal plants, are reported to be attacked by various replanting diseases. Therefore, replanting disease incidence has resulted in a tremendous hurdle to obtain maximum agricultural production of R. pseudostellariae.

The root exudates of R. pseudostellariae cause deterioration of the microbial community in the rhizosphere, increasing host-specific pathogens at the expense of beneficial microorganisms. We found the effect of phenolic acids and organic acids were invoked as a driver of the changes seen in the rhizosphere soils. We studied the effects of artificially applied root exudates of R. pseudostellariae on R. pseudostellariae seedling growth, rhizosphere soil microbial communities, and soil physicochemical properties. The deep pyrosequencing and qRT-PCR analysis demonstrated that the treatment of phenolic acids significantly decreased the relative abundance of Trichoderma, Penicillium, Pseudonocardiales, Xanthomonadales, Streptomycetales. And the organic acids had significantly negative effects on the relative abundance of Pseudonocardiales and Streptomycetales, which significantly increased the abundance of Fusarium, Xanthomonadales, Micrococcales and Gemmatimonadales. The non-invasive micro-test technique (NMT) analysis indicated that the root exudates increased the H+ efflux in the pathogenic fungi (Fusarium oxysporum and Talaromyces helicus) and decreased it in the beneficial fungi (Trichoderma harzianum), which creates an acid environment that inhibited proliferation of beneficial bacteria and facilitated build-up of specialized plant pathogens. This study explains the reasons why the root exudates are able to mediate a microflora shift and structure disorder in continuously monocultured R. pseudostellariae rhizosphere soil.