Entomology and Nematology Department, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, United States of America.
PLoS One. 2012;7(6):e38146. doi: 10.1371/journal.pone.0038146. Epub 2012 Jun 27.
While the role of herbivore-induced volatiles in plant-herbivore-natural enemy interactions is well documented aboveground, new evidence suggests that belowground volatile emissions can protect plants by attracting entomopathogenic nematodes (EPNs). However, due to methodological limitations, no study has previously detected belowground herbivore-induced volatiles in the field or quantified their impact on attraction of diverse EPN species. Here we show how a belowground herbivore-induced volatile can enhance mortality of agriculturally significant root pests. First, in real time, we identified pregeijerene (1,5-dimethylcyclodeca-1,5,7-triene) from citrus roots 9-12 hours after initiation of larval Diaprepes abbreviatus feeding. This compound was also detected in the root zone of mature citrus trees in the field. Application of collected volatiles from weevil-damaged citrus roots attracted native EPNs and increased mortality of beetle larvae (D. abbreviatus) compared to controls in a citrus orchard. In addition, field applications of isolated pregeijerene caused similar results. Quantitative real-time PCR revealed that pregeijerene increased pest mortality by attracting four species of naturally occurring EPNs in the field. Finally, we tested the generality of this root-zone signal by application of pregeijerene in blueberry fields; mortality of larvae (Galleria mellonella and Anomala orientalis) again increased by attracting naturally occurring populations of an EPN. Thus, this specific belowground signal attracts natural enemies of widespread root pests in distinct agricultural systems and may have broad potential in biological control of root pests.
虽然食草动物诱导挥发物在植物-食草动物-天敌相互作用中的作用在上层土壤中已有充分的记录，但新的证据表明，地下挥发物的排放可以通过吸引昆虫病原线虫（EPN）来保护植物。然而，由于方法学上的限制，以前没有研究在野外检测到地下食草动物诱导的挥发物，也没有量化它们对吸引多种 EPN 物种的影响。在这里，我们展示了地下食草动物诱导的挥发物如何增强农业上重要的根害虫的死亡率。首先，我们实时鉴定了在 Diaprepes abbreviatus 幼虫取食 9-12 小时后，从柑橘根中产生的前吉杰烯（1,5-二甲基环十二烷-1,5,7-三烯）。该化合物也在野外成熟柑橘树的根区中被检测到。从象鼻虫受损的柑橘根中收集的挥发物的应用吸引了本地 EPN，并与柑橘园中的对照相比，增加了甲虫幼虫（D. abbreviatus）的死亡率。此外，田间应用分离的前吉杰烯也导致了类似的结果。定量实时 PCR 显示，前吉杰烯通过吸引野外四种自然发生的 EPN，增加了害虫的死亡率。最后，我们通过在蓝莓田中应用前吉杰烯来测试这种根区信号的普遍性；幼虫（家蚕和东方金龟）的死亡率再次通过吸引自然发生的 EPN 种群而增加。因此，这种特定的地下信号可以吸引不同农业系统中广泛存在的根害虫的天敌，并且在根害虫的生物防治中可能具有广泛的潜力。
