Abstract:To screen allelochemicals in the continuous cropping of American ginseng, non-targeted metabolomics technology based on liquid chromatography-mass spectrometry(LC-MS) was used to analyze the rhizosphere soil of American ginseng treated with distilled water(CK), root extract(GT) and rhizosphere soil extract(ST) from 4-year-old American ginseng, respectively. The results showed that 44 differential metabolites were identified by mass spectrometry, of which 22 differential metabolites were VIP>1.4 and P<0.001. These differential metabolites included saponins, alkaloids, ketones and flavonoids, organic acids, terpenes, alcohols and coumarins. Additionally, the differential metabolites Ginsenoside Rg3, Ginsenoside Rg2, Indole-3-acetic acid, Methyl indole-3-acetate, Marmesin, Cytisine and Senecionine were further verified by HPLC. The data showed that the changes in the content of these 7 metabolites were found to be consistent with the results of metabolomics detection. The contents of Ginsenoside Rg3, Ginsenoside Rg2 and Methyl indole-3-acetate in GT group and the contents of Indole-3-acetic acid, Methyl indole-3-acetate, Marmesin, and Senecionine in ST group were significantly increased compared with the CK group, however, the content of Cytisine was significantly deceased.These seven metabolites had different degrees of allelopathic inhibition on cabbage seed germination and their roots and stems growth through allelopathic analysis. The results of this study indicated that the metabolites secreted into the soil during the continuous cropping of American ginseng may be the potential allelochemicals leading to the occurrence of continuous cropping obstacles of American ginseng. |