摘要:
野生状态下的东北红豆杉极少受病虫危害，为了探索其抗虫机理，采用浸渍叶碟法分别测定了东北红豆杉次生代谢化合物三尖杉宁碱和紫杉醇对舞毒蛾幼虫的选择性和非选择性拒食活性。结果表明，三尖杉宁碱和紫杉醇对舞毒蛾幼虫均具有拒食活性。高浓度的三尖杉宁碱的选择性和非选择性拒食率均高于低浓度的，当浓度为 2 mg/mL时，其非选择性拒食活性可达67.46 %，选择性拒食活性可达72.37%。紫杉醇在低浓度时就表现出较好的拒食活性，当浓度为0.25 mg/mL时，非选择性拒食率就达87.18%；当浓度低于1 mg/mL时，选择性拒食活性随着处理时间的推移而降低；当浓度高于1 mg/mL时，选择性拒食活性随着处理时间的推移而增强，在48 h时，拒食率可达74.95%。总体来看，紫杉醇对舞毒蛾幼虫的拒食效果要好于三尖杉宁碱。该研究结果部分解释了东北红豆杉不遭受昆虫危害的原因。
Abstract:
The wild populations of yew trees in northeastern China are rarely attacked by insects and diseases. To better understand its defense mechanism behind such phenomenon, potential antifeeding activity of two key secondary metabolic compounds of yew, cephalomannine and taxol, were tested against Lymantria dispar L. larvae in both “selective” and “non-selective” birch leaf disc bioassays. Our results showed that both cephalomannine and taxol exhibited significant antifeeding effect on L. dispar larvae. The antifeedancy of cephalomannine seemed to increase with its concentration in a dose-responsive fashion in both the “selective” and “non-selective” tests, reaching 67.46% and 72.37%, respectively, at 2 mg/mL. In contrast, taxol showed a very strong antifeeding effect even at the lowest concentration tested, reaching 87.18% of antifeedancy in “no-selective” test at 0.25 mg/mL. In the “selective” bioassay, the antifeeding activity of taxol seemed to decrease with the feeding time at 1 mg/mL or lower, but increased with the time at higher concentrations (1 mg/mL),reaching 74.95% after 48 h. In general, taxol showed stronger antifeeding activity against L. dispar larvae than did the cephalomannine. The significant antifeeding activity of the two metabolic compounds of yew, especially taxol, might partially explain why the yew trees are not or rarely attacked by insects.
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