Secondary metabolites commonly play important physiological roles in plants and can be modified quantitatively and qualitatively by exposure to biotic and abiotic interactions. Plant growth promoting rhizobacteria (PGPR) and herbivory induce systemic resistance. In the present study, we analyzed the induction of secondary metabolites in peppermint plants in response to chewing insect herbivory on PGPR-inoculated Mentha piperita plants. The secondary metabolites of M. piperita plants were increased when plants were inoculated with PGPR and also exposed to caterpillar herbivory. It was found that the total essential oil yield in inoculated plants with insect damage was ~2.6-fold higher than in controls. The yield was similar to that of plants either damaged by insects or inoculated, indicating that there was no synergism. The same trend was observed for phenolic compounds. In contrast, VOC emissions were significantly higher in plants infested by insects, independent of whether they were inoculated. Insect damaged plants had 5.5 times higher monoterpene emissions than control plants, and ~ 2-fold higher emissions than on PGPR-inoculated plants without insects. To gain a better understanding of how herbivory on PGPR-inoculated plants can cause an increase in secondary metabolites of peppermint, we examined changes in plant defense hormones in inoculated plants after herbivory. We found that the combination of both treatments increased the endogenous jasmonic and salicylic acid levels to the same extent as in plants only inoculated or only insect-damaged. Because different interactions can alter the phytochemistry of plants such as M. piperita, this topic is both ecologically and economically relevant.

中文翻译：

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土壤根瘤菌接种和咀嚼昆虫的食草性对薄荷脑叶次生代谢产物的影响。

次生代谢产物通常在植物中起重要的生理作用，并且可以通过暴露于生物和非生物相互作用来定量和定性地进行修饰。促进根际细菌生长的植物（PGPR）和食草动物引起系统性抗性。在本研究中，我们分析了薄荷植物中次级代谢产物的诱导，以响应PGPR接种的薄荷薄荷植物上的咀嚼昆虫食草。胡椒分枝杆菌的次生代谢产物当植物接种PGPR并暴露于毛虫食草时，植物数量增加。结果发现，带有昆虫危害的接种植物的总精油产量比对照高约2.6倍。产量与被昆虫破坏或接种的植物相似，表明没有协同作用。对于酚类化合物也观察到了相同的趋势。相比之下，受昆虫侵染的植物中的VOC排放量要高得多，而与是否进行了接种无关。受到昆虫破坏的植物的单萜排放量是对照植物的5.5倍，比没有昆虫的PGPR接种植​​物高约2倍。为了更好地了解接种PGPR的植物上的食草性如何引起薄荷次生代谢产物的增加，我们研究了食草后接种植物中植物防御激素的变化。我们发现，两种处理方法的结合使内源性茉莉酸和水杨酸的水平增加到与仅接种或仅被昆虫破坏的植物相同的程度。因为不同的相互作用会改变植物的植物化学特性，例如M. piperita，这个主题在生态和经济上都是相关的。