Knudsen Geir K, Norli Hans R, Tasin Marco
Division of Biotechnology and Plant Health, Norwegian Institute of Bioeconomy Research, Oslo, Norway.
Integrated Plant Protection, Department of Plant Protection Biology, Swedish University of Agricultural Science, Alnarp, Sweden.
Front Plant Sci. 2017 Dec 22;8:2206. doi: 10.3389/fpls.2017.02206. eCollection 2017.
Volatiles emitted by plants convey an array of information through different trophic levels. Animals such as host-seeking herbivores encounter plumes with filaments from both host and non-host plants. While studies showed a behavioral effect of non-host plants on herbivore host location, less information is available on how a searching insect herbivore perceives and flies upwind to a host-plant odor plume within a background of non-host volatiles. We hypothesized here that herbivorous insects in search of a host-plant can discriminate plumes of host and non-host plants and that the taxonomic relatedness of the non-host have an effect on finding the host. We also predicted that the ratio between certain plant volatiles is cognized as host-plant recognition cue by a receiver herbivorous insect. To verify these hypotheses we measured the wind tunnel response of the moth to the host plant rowan, to non-host plants taxonomically related (Rosaceae, apple and pear) or unrelated to the host (Pinaceae, spruce) and to binary combination of host and non-host plants. Volatiles were collected from all plant combinations and delivered to the test insect via an ultrasonic sprayer as an artificial plume. While the response to the rowan as a plant was not affected by the addition of any of the non-host plants, the attraction to the corresponding sprayed headspace decreased when pear or apple but not spruce were added to rowan. A similar result was measured toward the odor exiting a jar where freshly cut plant material of apple or pear or spruce was intermixed with rowan. Dose-response gas-chromatography coupled to electroantennography revealed the presence of seven field attractive and seven background non-attractive antennally active compounds. Although the abundance of field attractive and of some background volatiles decreased in all dual combinations in comparison with rowan alone, an increased amount of the background compounds (3E)-4,8-Dimethyl-1,3,7-nonatriene ((E)-DMNT) and (Z)-3-hexenyl acetate was found in the rowan-apple and rowan-pear but not in the rowan-spruce headspace. A higher ratio between the abundance of each field attractive component and that of (E)-DMNT and (Z)-3-hexenyl acetate was measured for rowan and rowan-spruce in contrast to rowan-pear and rowan-apple headspaces. Our result suggests that the ratio between field attractive and background antennaly active volatiles encodes host-plant recognition in our study system.
植物释放的挥发性物质通过不同营养级传递一系列信息。诸如寻找寄主的食草动物等动物会遇到来自寄主植物和非寄主植物的丝状气味羽流。虽然研究表明非寄主植物对食草动物寻找寄主有行为影响，但关于搜寻中的食草昆虫如何在非寄主挥发性物质的背景下感知并逆风飞向寄主植物气味羽流的信息较少。我们在此假设，寻找寄主植物的食草昆虫能够区分寄主植物和非寄主植物的气味羽流，并且非寄主植物的分类学亲缘关系会对找到寄主产生影响。我们还预测，某些植物挥发性物质之间的比例被取食的食草昆虫视为寄主植物识别线索。为了验证这些假设，我们测量了蛾在风洞中对寄主植物花楸、分类学上与寄主相关（蔷薇科，苹果和梨）或不相关（松科，云杉）的非寄主植物以及寄主和非寄主植物二元组合的反应。从所有植物组合中收集挥发性物质，并通过超声波喷雾器作为人工气味羽流传递给受试昆虫。虽然作为一种植物，花楸的反应不受任何非寄主植物添加的影响，但当向花楸中添加梨或苹果而非云杉时，对相应喷雾顶空的吸引力降低。对于装有新鲜切割的苹果或梨或云杉与花楸混合的植物材料的罐子散发的气味，也测量到了类似结果。剂量 - 反应气相色谱 - 触角电位联用技术揭示了七种田间有吸引力和七种背景无吸引力的触角活性化合物的存在。尽管与单独的花楸相比，所有二元组合中田间有吸引力的化合物和一些背景挥发性物质的丰度都降低了，但在花楸 - 苹果和花楸 - 梨的顶空中发现背景化合物（3E） - 4,8 - 二甲基 - 1,3,7 - 壬三烯（（E） - DMNT）和乙酸（Z） - 3 - 己烯酯的量增加，而在花楸 - 云杉顶空中未发现。与花楸 - 梨和花楸 - 苹果顶空相比，花楸和花楸 - 云杉中每种田间有吸引力成分与（E） - DMNT和乙酸（Z） - 3 - 己烯酯丰度之间的比例更高。我们的结果表明，在我们的研究系统中，田间有吸引力和背景触角活性挥发性物质之间的比例编码了寄主植物识别。
