两近缘种夜蛾对低浓度烟草挥发物的触角电位反应

Electroantennogram responses of two sibling Helicoverpa species to tobacco plant volatile compounds at a lower concentration

寡食性的烟夜蛾Helicoverpa assulta(Guene)和广食性的棉铃虫Helicoverpa armigera(Hbner)是实夜蛾属的2近缘种昆虫,在它们的寄主植物中,只有烟草为其共同寄主,为明确它们对烟草挥发物嗅觉感受能力的差异,测定了这2种夜蛾的处女雌蛾、交配雌蛾及雄蛾对20种低浓度(1.0×10-5mol.L-1)烟草挥发物的触角电位反应,并对其中6种化合物进行了剂量反应测定,结果表明,(1)2种夜蛾对测试化合物均可产生EAG反应且反应趋势相似:对植物中普遍存在的绿叶气味、脂肪族和芳香族化合物的反应显著高于具有烟草"种"特异性的单萜类、倍半萜类和杂环化合物,表明2种夜蛾远距离定向时,对植物"种"的辨识能力均较差。(2)2种夜蛾对脂肪族C6_化合物的EAG反应最强,碳链延长或缩短都会导致反应强度的降低。(3)烟夜蛾对大多数化合物的EAG反应大于棉铃虫,表明在远距离寄主定向时其嗅觉感受器对寄主挥发物的感受能力强于棉铃虫。(4)烟夜蛾交配雌蛾对β-水芹烯和桧烯的EAG反应高于其处女雌蛾和雄蛾,除此之外2种夜蛾的EAG反应未见显著的性别差异,推测β-水芹烯和桧烯可能是烟夜蛾在烟草上产卵的"信号"物质。(5)剂量反应曲线表明,在测试的浓度范围内,2种夜蛾对6种类型化合物的EAG反应强度与其浓度呈正相关,且均未达到饱和。由此可知,与棉铃虫相比,烟夜蛾嗅觉神经系统在其寄主定向行为中所起的作用更重要、也更专化。

Oligophagous Helicoverpa assulta （Guenée） and polyphagous H. armigera （Hübner） are two sibling species. Among their host plants, tobacco is the only one they share and coexist on. In order to further understand the ability difference in their olfactory orientation to tobacco volatiles, electroantennograms （EAG） were recorded from virgin and mated females, as well as males, of the two sibling species in responses to 20 tobacco volatile compounds at a low concentration （1.0×10^-5 mol·L^-1）, and EAG dose-response curves were also constructed for 6 compounds. The results showed that： （1） Both H. assulta and H. armigera elicited similar EAG responses to the tested compounds, i.e., both species were more sensitive to the general odor componds, such as green leaf volatiles, aliphatic and aromatic compounds, than to the specific odor components of tobacco, such as monoterpenes, sesquiterpenes and heterocyclic compounds, suggesting that both species have the weak capability in distiguishing specific plant species from a distance. （2） The EAG responses of both insect species were maximal to the C6 aliphatic compounds, and declined as the carbon chain-length of compounds increased or decreased. （3） H. assulta elicited higher EAG responses to the most tested compounds than H. armigera, indicating that the olfactory sensilla of H. assulta are more sensitive to the host volatile compounds than H. armigera in their host orientation from a long distance. （4） In general, there were no significant sexual differences in their EAGs of the two sibling species, but the mated females of H. assulta elicited stronger EAG responses to β-phellandrene and sabinene hydrate than virgin females or males, implying that β-phellandrene and sabinene hydrate might be the ovipositional semiochemicals of H. assulta on tobacco plants. （5） The result of EAG dose-response curves indicated that EAG responses of both insect species were dose-dependent to 6 types of compounds in the tested concentration range, far from their maximum responses. In conclusion, these results indicated that the olfactory neural system of H. assulta is more specialized and plays more important roles in host orientation behaviors than that of H. armigera.