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.

Deciphering Plant-Insect-Microorganism Signals for Sustainable Crop Production

“…In addition to direct microbial colonisation, plant responses to microbial VOCs can influence plant resistance to herbivores. VOCs from the soil-borne fungus F. oxysporum induced phenotypic responses of Brassica rapa , which differentially affected the performance of the root herbivores Heterodera schachtii and the cabbage root fly D. radicum [ 145 ]. The identity of the source of microbial VOCs is important to determine the effects on the outcome of plant-insect interactions.…”

Fungal endophytes of Brassicaceae: Molecular interactions and crop benefits

“…One example is T. harzianum, which reduces the disease caused by Meloidogyne incognita in turnip plants, although the mechanism of action involved is unknown (Ibrahim et al, 2012). In wild turnip plants, root colonization by the endophyte F. oxysporum caused a slowdown in the development of the root nematode cysts, Heterodera schachtii, due to the volatiles emitted by the fungus (Moisan et al, 2021). Some endophytic fungi of Brassicaceae crops can act directly on insect-pest larvae by parasitism, as they are present in the plant tissues consumed by them.…”

Volatile organic compounds shape belowground plant–fungi interactions

“…Volatiles emitted by the pathogenic fungi R. solani and F. oxysporum f. sp. raphani decrease the root growth rate of B. rapa seedlings ( Moisan et al., 2021 ).…”

“…In addition, volatiles produced by soilborne fungi can affect nematode development and behavior. Volatiles emitted by some F. oxysporum strains inhibit egg hatch in the root-knot nematode Meloidogyne incognita and slow development of the cyst nematode Heterodera schachtii ( Terra et al., 2018 ; Moisan et al., 2021 ). Thus, volatiles from soilborne fungi not only negatively affect or modulate plant growth but also diffuse through the soil matrix to help plants attract disease antagonists or natural enemies for defense.…”