Endomelanconiopsis microspora发酵产物乙酸乙酯提取物对人参核盘菌的抑制机理

【背景】人参菌核病是人参的主要病害之一，严重影响人参的产量。【目的】探索白花蒲公英内生菌(Endomelanconiopsis microspora)发酵产物乙酸乙酯提取物对人参核盘菌的抑制机理。【方法】采用人参核盘菌菌丝生长和孢子萌发试验测定抑制效果；采用显微镜观察菌丝形态变化，通过电导率和核酸含量的变化测定细胞膜通透性，通过丙二醛(malondialdehyde，MDA)含量和超氧化物歧化酶(superoxide dismutase，SOD)、过氧化物酶(peroxidase，POD)和过氧化氢酶(catalase，CAT)活力的变化测定膜脂过氧化程度。【结果】内生菌E. microspora发酵产物乙酸乙酯提取物能显著抑制人参核盘菌菌丝生长，最小抑菌浓度为3.75 mg/mL，培养6 d后抑制率为76.22%。该提取物能显著抑制人参核盘菌孢子萌发，15.00 mg/mL时抑制效果最好，抑制率达90.69%。提取物影响菌丝形态，增加人参核盘菌细胞膜通透性，造成菌丝内含物外渗，7.50 mg/mL处理10 h后电导率和核酸含量分别比对照组增加30.11%和62.85%。同时提取物显著增加人参核盘菌MDA含量和SOD、POD、CAT活力，7.50 mg/mL处理组呈现先上升后下降的变化趋势，并在12 h时达到最高值。【结论】内生菌E. microspora发酵产物乙酸乙酯提取物通过改变人参核盘菌细胞膜通透性，加剧膜脂过氧化，破坏细胞膜完整性，导致细胞内含物流失，显著抑制孢子萌发和菌丝生长。

Ethyl acetate extract of Endomelanconiopsis microspora inhibits Sclerotinia ginseng

Background] Sclerotinia ginseng, one of the major pathogen attacking ginseng, seriously affects the yield of ginseng. Objective] To explore the mechanism of ethyl acetate extract of the endophytic bacteria Endomelanconiopsis microspora from Taraxacum albiflos Kirschner & Štepanek in inhibiting S. ginseng. Methods] The inhibitory effect was verified by the test of mycelial growth and spore germination of S. ginseng. The morphological changes of mycelia were observed under a microscope. The cell membrane permeability was detected by changes in conductivity and nucleic acid content, and the membrane lipid peroxidation was measured by changes in malondialdehyde (MDA) content and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. Results] The ethyl acetate extract from E. microspora significantly inhibited the mycelial growth of S. ginseng with the minimum inhibitory concentration (MIC) of 3.75 mg/mL and the inhibition rate of 76.22% after 6 days of culture. The ethyl acetate extract significantly inhibited the spore germination of S. ginseng. The 15.00 mg/mL ethyl acetate extract demonstrated the optimal inhibitory effect with the inhibition rate of 90.69%. The ethyl acetate extract influenced mycelial morphology, increased cell membrane permeability of S. ginseng, and resulted in extravasation of mycelial inclusions. Compared with the control group, the treatment with 7.50 mg/mL ethyl acetate extract for 10 h increased the conductivity and nucleic acid content by 30.11% and 62.85%, respectively. At the same time, the ethyl acetate extract significantly increased MDA content and SOD, POD and CAT activities of S. ginseng. The MDA content and SOD, POD and CAT activities in the 7.50mg/mL treatment group first increased, peaked at the time point of 12 h, and then decreased. Conclusion] The ethyl acetate extract from the endophytic bacteria E. microspora changed the cell membrane permeability of S. ginseng, aggravated the membrane lipid peroxidation, and destroyed the cell membrane integrity, thus leading to the loss of cell inclusions and inhibiting the spore germination and mycelial growth.