6株马铃薯内生真菌拮抗病原菌的物质基础及作用机制研究

The Potato's Staple Food Strategy is crucial for the National Food Security and Farmers' Income Increase. However, the production and quality of potatoes are severely affected by various pathogenic fungal infections, involving Phytophthora infestans (Potato Late Blight), Alternaria solani (Potato Early Blight), Rhizoctonia solani (Potato Black Scurf) and Fusarium oxysporum (Potato Blight). Chemical fungicides e.g. metalaxyl-mancozeb and oxadixyl mancozeb, are the major prevention methods; however, their application is limited due to the “3R1P”, namely, residue, resistant, resurgence and pollution. Potato endophytic fungi are fascinating sources for novel fungicides with different mechanism. According to the previous investigation, a series of natural products including drechmerins, amphotericins, colletotrichones, periconicins and diaportheins were isolated from diverse endophytic fungi, and revealed with potent anti-pathogenic activity. In our previous study, 493 strains of endophytic fungi were isolated and authenticated from the whole plants of potatoes grown in different places. The preliminary anti-pathogenic fungi screening against the four main pathogenic fungi of potato, P. infestans, A. solani, R. solani and F. oxysporum, yielded 6 strains of fungi (Bipolaris eleusines, Chaetomium pseudoglobosum, Trichothecium crotocinigenum, Xylaria curta, Talaromyces trachyspermus, Albifimbria viridis) with high antifungal potency. The subsequent investigation on the culture of B. eleusines gave rise to 6 new sesquiterpenes, bipolenins A-F (1-6), and ten known ones, isosativenediol (7), dihydroprehelminthosporol (8), helminthosporol (9), drechslerines C (10), drechslerine A (11), secolongifolene diol (12), cis-sativenediol (13), prehelminthosporol (14), prehelminthosporolactone (15) and victoxinine (16). Their structures were elucidated by extensive spectroscopic analyses. Compounds 2, 6, 9, 10 and 15 showed obvious inhibition on four pathogenic fungi, P. infestans, A. solani, R. solani and F. oxysporum, with inhibition rates higher than 60% at the concentration of 10μM. The structure-activity relationship study suggested that their antimicrobial activity was closely related to the tetrahydro-2H-pyran moiety in the structure. Therefore, it will be very interesting to clarify the antifungal active constituents and their mechanism. In this project, the cultivation condition of the 6 fungi will be optimized by changing the medium and parameters; then the fungus will be cultured under the optimal condition in large scale; systematically chemical and biological investigation will be conducted on the yielded fermentation broth to reveal the active constituents; the antifungal mechanism will be further studied for the discovery of novel fungicide candidates. The successful implementation of this project (if granted) will provide scientific basis not only for clarifying the antifungal components in potato endophytic fungi but also for searching novel pathogenic fungi inhibitors with different mechanism.

马铃薯主粮化战略是保障国家粮食安全和农民增收的重要举措，然而其产量和品质深受真菌病害影响。现有化学防治手段易产生“3R1P”，环境友好性差，马铃薯内生真菌是新型病原真菌抑制剂的重要来源。我们前期从不同产地马铃薯中分离鉴定493株内生真菌，采用平板对峙法和打孔法筛选出6株高活性真菌B.eleusines、C.pseudoglobosum、T.crotocinigenum、X.curta、T.trachyspermus、A.viridis，可显著抑制马铃薯晚疫病、早疫病、黑痣病和枯萎病四种主要致病菌。对B.eleusines开展初步研究，从中分离鉴定16个倍半萜，包括6个新化合物，5个活性成分（10μM）对四种病原菌抑制率均大于60%，其活性与结构中六元氧环密切相关。本研究将在前期基础上，深入开展上述6株拮抗内生真菌的抗病原菌活性成分和作用机制研究，为新型马铃薯致病菌天然抑制剂的发现奠定基础。

马铃薯主粮化战略是保障国家粮食安全和农民增收的重要举措，然而其产量和品质深受真菌病害影响。现有化学防治手段易产生“3R1P”，环境友好性差，马铃薯内生真菌是新型病原真菌抑制剂的重要来源。我们以前期筛选出的6株高活性内生真菌为研究对象，采用植物化学手段对内生真菌发酵液进行了化学成分研究，分离出了69个单体化学成分，通过NMR、MS、UV、IR等波谱学技术鉴定了其中52个化合物的化学结构，包括3个新化合物。选取其中13个含量较大的化合物进行了抗病原真菌活性筛选，发现4个化合物对尖孢镰刀菌（Fusarium oxysporum）和致病疫霉（Phytophthora infestans）表现出一定的拮抗作用。对活性最好的化合物2,5-二羟基甲苯进行抗菌机制研究，发现化合物2,5-二羟基甲苯可导致尖孢镰刀菌细胞壁溶解破裂，从而抑制其生长。本研究初步揭示了马铃薯内生真菌抗病原真菌的物质基础及作用机理，为后期深入研究开发马铃薯真菌病害生物源抑制剂奠定了前期基础。