【目的】鉴定黄蜻幼虫肠道中具有除草活性的真菌,并分析其除草活性成分。【方法】通过形态学观察和分子生物学5.8S r DNA-ITS序列分析,明确菌株QTYC-51的分类地位。结合培养皿生物分析法测定菌株发酵液和单体化合物的除草活性,采用色谱方法从该菌乙酸乙酯粗提物中分离活性成分,并利用质谱和核磁共振谱鉴定活性物质。【结果】菌株QTYC-51被鉴定为拟盾壳霉属菌(Paraconiothyrium sp.),其发酵液对稗草和反枝苋幼根生长有较好的抑制作用,抑制率分别为76.9%和56.5%。从QTYC-51发酵产物中分离到5个单体化合物,分别为1,8-dihydroxyanthraquinone,1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione,hydroxyvertixanthone,globosuxanthone和1,3,6,8-tetrahydroxyanthraquinone。在供试浓度为100μg/m L时,化合物globosuxanthone对稗草和反枝苋幼根生长有明显的抑制作用,抑制率分别为94.1%和79.0%,与阳性对照2,4-二氯苯氧乙酸效果相当;化合物1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione具有较好的除草活性,对稗草和反枝苋幼根的生长抑制率分别为50.3%和58.6%。【结论】菌株QTYC-51具有开发为微生物源除草剂的潜能。
Three main phytotoxic compounds including lunatoic acid A （1）, 5Z-7-oxozeaenol （2） and zeaenol （3） were isolated from the fermentation broth of Cladosporium oxysporum DH14, a fungus residing in the locust （Oxya chinensis ） gut. Two additional derivative compounds, compound la and lb, were synthesized by methylation and chlorination of compound 1, respectively. The structures of such compounds were identified on the basis of spectroscopic analysis and by comparison of the corresponding data to those previously reported in the literature. Compounds 1-3 exhibited significantly phytotoxic activities against the radicle growth of Amaranthus retroflexus L. with the 50% inhibitory concentrations （ICso values） of 4.51, 4.80 and 8.16 μg· mL^-1, respectively, which is comparable to that positive control 2,4-dichlorophenoxyacetic acid （IC50=1.95 μg· mL^-1）. Furthermore, the compound 1 showed selective phytotoxic activity with the inhibition rate of less than 22% against the crops of Brassica rapa L., Sorghum durra, Brassica campestris L,, Capsicum annucm and Raphanus safivus L. under the concentration of 100 μg· mL^-1 Both derivatives of compound 1 had moderate phytotoxic activity against the radicle growth of A. retroflexus L. The findings of our present study suggest that these compounds provide new promising candidates for the potential management strategies of weeds.
LU Yi-huiLI ShuaiSHAO Ming-weiXIAO Xiao-huiKONG Li-chunJIANG Dong-huaZHANG Ying-lao
