Exposure to herbivore-induced plant volatiles (HIPVs) is known to enhance the defense responses in plants. This so-called priming effect has only been marginally studied in intercropping systems. We tested whether HIPVs from cowpea, which often serves as an intercrop alongside maize, can prime herbivore-induced volatile emissions in maize. Conventional volatile collection assays and real-time mass spectrometry revealed that maize plants that were exposed to HIPVs from cowpea infested with Spodoptera exigua caterpillars emitted more than control plants when they themselves were subsequently damaged by the same pest. The enhanced emission was only evident on the first day after infestation. Maize plants that were exposed to HIPVs from cowpea infested by S. frugiperda larvae showed no priming effect and released considerably less upon S. frugiperda infestation than upon S. exigua infestation. The latter may be explained by the fact that S. frugiperda is particularly well adapted to feed on maize and is known to suppress maize HIPV emissions. Our results imply that HIPVs from cowpea, depending on the inducing insect herbivore, may strongly prime maize plants. This deserves further investigation, also in other intercropping systems, as it can have important consequences for tritrophic interactions and crop protection.

众所周知，接触食草动物诱导的植物挥发物（HIPV）会增强植物的防御反应。这种所谓的启动效应在间作系统中只得到了少量研究。我们测试了来自豇豆（通常与玉米一起作为间作作物）的 HIPV 是否可以引发食草动物引起的玉米挥发性排放。传统的挥发物收集分析和实时质谱分析表明，暴露于感染了甜菜夜蛾毛虫的豇豆的 HIPV 的玉米植株在随后受到相同害虫损害时比对照植株排放更多。仅在感染后的第一天，排放量的增加才明显。暴露于来自被草地贪夜蛾幼虫侵染的豇豆的HIPV的玉米植物没有表现出启动效应，并且在草地贪夜蛾侵染时释放的HIPV比在甜菜夜蛾侵染时释放的要少得多。后者的原因可能是，草地贪夜蛾特别适合以玉米为食，并且已知可以抑制玉米的 HIPV 排放。我们的结果表明，来自豇豆的 HIPV（取决于诱导昆虫草食动物）可能会强烈引发玉米植物。这值得进一步研究，在其他间作系统中也是如此，因为它可能对三营养相互作用和作物保护产生重要影响。