Liu Chia-Ming, Matsuyama Shigeru, Kainoh Yooichi
Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, 305-8572, Japan.
Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki, 305-8572, Japan.
J Chem Ecol. 2019 Aug;45(8):684-692. doi: 10.1007/s10886-019-01088-y. Epub 2019 Jul 10.
Herbivore-induced plant volatiles (HIPVs) are important cues for natural enemies to find their hosts. HIPVs are usually present as blends and the effects of combinations of individual components are less studied. Here, we investigated plant volatiles in a tritrophic system, comprising the parasitoid wasp Lytopylus rufipes Nees (Hymenoptera: Braconidae), the Oriental fruit moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae), and Japanese pear, Pyrus pyrifolia 'Kosui', so as to elucidate the effects of single components and blends on wasp behaviors. Bioassays in a four-arm olfactometer, using either shoots or their isolated volatiles collected on adsorbent, revealed that female wasps preferred volatiles from host-infested shoots over those from intact shoots. Analyses identified (Z)-3-hexenyl acetate (H), linalool (L), (E)-β-ocimene (O), (E)-3,8-dimethyl-1,4,7-nonatriene (D), and (E,E)-α-farnesene (F). Among them, only F was induced by infestation with G. molesta. When tested singly, only O and D elicited positive responses by L. rufipes. Binary blends of HO and DF elicited a positive response, but that of HD elicited a negative one, even though D alone elicited a positive response. Remarkably, wasps did not prefer either the ODF or HL blends, but showed a highest positive response to a quinary blend (HLODF). These results show that synergism among volatiles released from host-infested plants is necessary for eliciting high behavioral responses in L. rufipes, enabling L. rufipes to find its host efficiently.
植食性昆虫诱导植物释放的挥发物（HIPVs）是天敌寻找寄主的重要线索。HIPVs通常以混合物的形式存在，而对单个成分组合的影响研究较少。在此，我们研究了一个三营养级系统中的植物挥发物，该系统包括寄生蜂红足丽旋小蜂（Lytopylus rufipes Nees，膜翅目：茧蜂科）、梨小食心虫（Grapholita molesta (Busck)，鳞翅目：卷蛾科）和日本梨品种幸水梨（Pyrus pyrifolia 'Kosui'），以阐明单个成分和混合物对寄生蜂行为的影响。在四臂嗅觉仪中进行的生物测定，使用吸附剂收集的嫩枝或其分离出的挥发物，结果表明雌性寄生蜂更喜欢寄主侵害嫩枝释放的挥发物，而不是完整嫩枝释放的挥发物。分析鉴定出了乙酸（Z）-3-己烯酯（H）、芳樟醇（L）、（E）-β-罗勒烯（O）、（E）-3,8-二甲基-1,4,7-壬三烯（D）和（E,E）-α-法尼烯（F）。其中，只有F是由梨小食心虫侵害诱导产生的。单独测试时，只有O和D能引起红足丽旋小蜂的阳性反应。HO和DF的二元混合物引起了阳性反应，但HD的二元混合物引起了阴性反应，尽管单独的D能引起阳性反应。值得注意的是，寄生蜂既不偏好ODF混合物也不偏好HL混合物，但对五元混合物（HLODF）表现出最高的阳性反应。这些结果表明，寄主侵害植物释放的挥发物之间的协同作用对于在红足丽旋小蜂中引发高行为反应是必要的，使红足丽旋小蜂能够有效地找到其寄主。
