Volatiles from the fungus Fusarium oxysporum affect interactions of Brassica rapa plants with root herbivores

Abstract

1. Soil is a diverse and heterogeneous environment where chemicals mediate numerous interactions between soil organisms and plants. To date, studies have extensively addressed volatile-mediated interactions between soil microorganisms and the effects of microbial volatiles on plant growth. Yet, to our knowledge, it remains to be explored whether volatiles from soil-borne fungi can influence plant interactions with root herbivores, facilitating or hampering performance of competitors that share the same host plant. 2. In the present study, we investigated the effects of volatiles emitted by the soil-borne fungus Fusarium oxysporum on the performance of two root herbivores: the plant parasitic cyst nematode, Heterodera schachtii, and the insect root herbivore, Delia radicum, upon infestation of Brassica rapa roots. 3. Fungal volatiles slowed down the development of the root nematode cysts but increased their size, suggesting an enhanced egg load. In contrast, the performance of the insect root herbivore was unaffected by the exposure of roots to fungal volatiles. Additionally, fungal volatiles promoted the growth of plants infested with the root nematode, but not of those infested with the insect root herbivore. 4. Together, our data show that volatiles from a soil-borne fungus can affect root interactions with root herbivores. Increased production of nematode eggs and plant growth promotion suggest a specific modulation of root-herbivore interactions by fungal volatiles.