Autotoxic Ginsenosides in the Rhizosphere Contribute to the Replant Failure of <i>Panax notoginseng</i>

Background and Aims Sanqi ginseng (Panax notoginseng) growth is often hampered by replant failure. In this study, we aimed to examine the role of autotoxicity in Sanqi replant failures and assess the role of ginsenosides in autotoxicity. Methods The autotoxicities were measured using seedling emergence bioassays and root cell vigor staining. The ginsenosides in the roots, soils, and root exudates were identified with HPLC-MS. Results The seedling emergence and survival rate decreased significantly with the continuous number of planting years from one to three years. The root exudates, root extracts, and extracts from consecutively cultivated soils also showed significant autotoxicity against seedling emergence and growth. Ginsenosides, including R1, Rg1, Re, Rb1, Rb3, Rg2, and Rd, were identified in the roots and consecutively cultivated soil. The ginsenosides, Rg1, Re, Rg2, and Rd, were identified in the root exudates. Furthermore, the ginsenosides, R1, Rg1, Re, Rg2, and Rd, caused autotoxicity against seedling emergence and growth and root cell vigor at a concentration of 1.0 µg/mL. Conclusion Our results demonstrated that autotoxicity results in replant failure of Sanqi ginseng. While Sanqi ginseng consecutively cultivated, some ginsenosides can accumulate in rhizosphere soils through root exudates or root decomposition, which impedes seedling emergence and growth.研究背景与目的 三七（Panax notoginseng）的生长常受重茬障碍（replant failure）困扰。本研究旨在探究自毒作用（autotoxicity）在三七重茬障碍中的作用，并评估人参皂苷（ginsenosides）在自毒作用中的功能。 方法 本研究通过幼苗萌发生物测定与根系细胞活力染色实验测定自毒活性；采用高效液相色谱-质谱联用（HPLC-MS）技术对根系、土壤及根系分泌物中的人参皂苷进行鉴定。 结果 随着连作年限从1年增至3年，三七的出苗率与存活率显著降低。根系分泌物、根系提取物以及连作土壤提取物均对幼苗萌发与生长表现出显著的自毒活性。在根系与连作土壤中鉴定出的人参皂苷包括R1、Rg1、Re、Rb1、Rb3、Rg2及Rd；而在根系分泌物中鉴定出的人参皂苷则为Rg1、Re、Rg2与Rd。此外，当浓度为1.0 μg/mL时，R1、Rg1、Re、Rg2及Rd可对幼苗萌发、生长及根系细胞活力产生自毒抑制作用。 结论 本研究结果证实，自毒作用是导致三七重茬障碍的核心原因。当三七连作时，部分人参皂苷可通过根系分泌物分泌或根系腐解在根际土壤中累积，进而阻碍幼苗萌发与生长。