Upon herbivory, plants emit specific herbivore‐induced plant volatiles (HIPVs) that can attract natural enemies of the herbivore thus serving as indirect plant resistance. Not only insect herbivores, but microorganisms may also affect HIPV emission before or after plant colonisation, which in turn can affect behaviour of natural enemies of the herbivore. Yet, it remains elusive whether volatiles from microorganisms influence HIPV emission and indirect plant resistance. In this study, we investigated whether exposure of Brassica rapa roots to volatiles from soil‐borne fungi influence HIPV emission and the recruitment of natural enemies of Pieris brassicae larvae. Using a two‐compartment pot system, we performed greenhouse and common‐garden experiments, and we profiled plant HIPV emission. We found that exposure of plant roots to fungal volatiles did not affect the number of P. brassicae larvae recollected from the plants, suggesting a neutral effect of the fungal volatiles on natural predation. Likewise, in a greenhouse, similar numbers of larvae were parasitised by Cotesia glomerata wasps on control plants as on fungal volatile‐exposed plants. Additionally, chemical analysis of HIPV profiles revealed no qualitative and quantitative differences between control plants and fungal volatile‐exposed plants that were both infested with P. brassicae larvae. Together, our data indicate that root exposure to fungal volatiles did not affect indirect plant resistance to an insect herbivore. These findings provide new insight into the influence of indirect plant resistance by fungal volatiles that are discussed together with the effects of fungal volatiles on direct plant resistance.

中文翻译：

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没有证据表明土传真菌的挥发物可以调节芸苔属植物的间接植物抗性

在食草时，植物会释放出特定的食草动物诱导植物挥发物 (HIPV)，可以吸引食草动物的天敌，从而起到间接植物抗性的作用。不仅昆虫食草动物，而且微生物也可能影响植物定植之前或之后的 HIPV 排放，这反过来又会影响食草动物天敌的行为。然而，微生物的挥发物是否影响 HIPV 排放和间接植物抗性仍然难以捉摸。在这项研究中，我们调查了芸苔根暴露于土传真菌的挥发物是否会影响 HIPV 的排放和青菜紫菜幼虫天敌的招募。使用双室盆栽系统，我们进行了温室和普通花园实验，并对植物 HIPV 排放进行了分析。我们发现植物根部暴露于真菌挥发物不会影响从植物中回收的芸苔藓幼虫的数量，表明真菌挥发物对自然捕食的中性影响。同样，在温室中，与真菌挥发物暴露的植物一样，对照植物上的 Cotesia glomerata 黄蜂寄生的幼虫数量相似。此外，HIPV 谱的化学分析显示，对照植物和暴露于真菌的挥发性暴露植物之间没有定性和定量差异，这两种植物都感染了 P. brasicae 幼虫。总之，我们的数据表明根部暴露于真菌挥发物不会影响植物对昆虫食草动物的间接抗性。