意大利苍耳入侵驱动土壤真菌群落结构变化的化学物质基础及其生态学意义

Elucidation of the invasion mechanism of exotic species remains a hot yet difficult research question. Chemicals produced by exotic plants can be metabolized as carbon sources by soil microorganisms which consequently will alter their community structure and function and create favorable plant-soil feedback (PSF), which is considered to be a key determinant involving in exotic plant invasion. However, being limited by interdiscipline, research on the chemistry foundation that causes the abovementioned phenomenon is still rather weak, which significantly constrains deep understanding of PSF mechanism. Our previous study revealed that the exotic plant Xanthium italicum accumulates pathogens such as fusarium sp. and reduces the abundance of Arbuscular mycorrhizal fungi, which promotes its invasion; However, it is still unclear how chemicals trigger this phenomenon and its subsequent ecological consequences. Based on our previous study on the isolation of allelochemiclas of X. italicum, we plan to combine the bioassay-guided fractionation method and the method of using known phytotoxins including sesquiterpenoids, phenolics and evaluate their activity on soil fungi that poses both negative and positive effects on plants; we will also analyze their concentration in plant materials and soils and test the effect of the shift of soil fungi on X. italicum and native plant species, which will eventually help elucidating the mechanism through which X. italicum release bioactive compounds into the soil, change the structure of soil microorganisms and create a specific environment that facilitates its invasion success.

外来植物入侵机理的解析是当前的研究热点和难点。入侵植物产生的化学物质被土壤微生物作为碳源分解利用，从而改变其群落结构和功能，可能就此形成有利于自身的植物-土壤反馈（PSF），这一机制被认为是决定外来植物入侵成功的重要原因。然而，受限于学科交叉，目前对引发此现象的化学物质根源的研究还十分薄弱，严重制约了对PSF发生机制的深入研究。我们在前期研究中发现，入侵植物意大利苍耳通过在土壤中富集病原菌和降低共生真菌AMF丰度来构建有利于自身的PSF，但对导致此现象的化学物质基础还缺乏了解。因此，本项目拟在前期对其化感物质研究的基础上，结合活性跟踪的系统分离法和应用已知化合物的方法确定影响土壤有害（病原菌）及有益（AMF等）真菌的活性化合物，分析其在植株和土壤中的分布动态，验证有害及有益真菌对入侵及本土植物影响的差异性，以期完整解析意大利苍耳通过释放特定化合物来建立有利的PSF的入侵机制。

意大利苍耳是近年来在我国危害严重的外来入侵植物，目前对其入侵机理并不清楚。前期研究发现，意大利苍耳在入侵地土壤中通过富集本土病原菌和降低本土植物依赖性强的有益真菌来创建对自身有利的生存环境，但是具体哪些次生代谢产物参与此过程尚不明确。本研究以两条不同的路线开展对活性次生代谢产物的鉴定工作：一条是从头开始的活性跟踪下的系统分离方法，另外一条是检测前期已鉴定的意大利苍耳化感物质活性的方法。通过第一条途径得到的主效活性物质是苍耳亭，通过第二条途径在验证了苍耳亭化感效应的同时，明确了意大利苍耳挥发油及阿魏酸的化感活性也符合预设，而苍耳皂素、黄质宁、甲氧基寿菊素、绿原酸、阿魏酸等化合物部分符合预设。据此我们推测意大利苍耳主要通过产生相对含量较高的苍耳亭类次生代谢产物，辅以挥发性成分及酚酸类化合物，共同作用于土壤微生物群落结构和功能，使其更加有利于自身的优势建立。我们的研究结构从意大利苍耳产生的化感物质与土壤真菌构建的植物-土壤反馈的角度对其入侵机理进行了解析，为深入了解该植物的成灾机制提供了科学依据。