Odours from friends and foes: ecological consequences of volatiles from soil-borne fungi on plant growth and defence against herbivores

Kay Moisan

Research output: Thesisinternal PhD, WU

Abstract

Volatiles, i.e. odours, play key roles in mediating ecological interactions within and between plants, animals and microorganisms. For example, it is well establishment nowadays that volatiles emitted by beneficial microorganisms can promote plant growth and enhance plant resistance to leaf pathogens. The overall aim of this PhD project was to investigate the effects of volatiles from soil-borne fungi on plant growth and defence against herbivores aboveground and belowground, and to assess whether plants distinguish between volatiles from pathogenic and non-pathogenic fungi.

We selected eleven soil-borne fungi: half of these fungi are potential pathogens of brassicaceous species, whereas the other fungi are saprophytes that co-occur with Brassicaceae plants. After testing in vitro exposure of Arabidopsis thaliana plants (thale cress) and in vivo exposure of Brassica rapa roots (wild turnip) to fungal volatiles, we showed that fungal volatiles can positively alter plant physiology by promoting plant growth and by accelerating plant flowering, regardless of the pathogenicity of the fungus. Interestingly, plant compensatory growth upon attack by an herbivore was also influenced by former root exposure to fungal volatiles, making plants more or less capable to endure the loss of tissues due to herbivory. Furthermore, plant exposure to fungal volatiles affected plant resistance to shoot and root herbivores, making plants more or less suitable for insect feeding. For instance, the performance of a leaf caterpillar was negatively or positively affected by certain fungal volatiles and root colonisation by plant-parasitic nematodes was enhanced upon exposure to volatiles of Fusarium oxysporum. Yet, plant indirect resistance (i.e. recruitment of natural enemies of the herbivores) was not altered by fungal volatiles. Intriguingly, although pathogenic and non-pathogenic fungi emitted distinct volatile organic compound profiles, plants did not seem to differentiate their friends from their foes. In contrast, we showed that roots of B. rapa seedlings were attracted to volatiles emitted by the root pathogen Rhizoctonia solani.

Collectively, the findings of this study highlight the importance of fungal volatiles for plant health by directly affecting plant growth and by modulating plant interactions with other organisms. Moreover, they raise fundamental questions about the evolutionary ecology of such interactions between roots and fungi, in particular with root pathogens.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Dicke, Marcel, Promotor
  • Raaijmakers, J.M., Promotor, External person
  • Cordovez, V., Co-promotor, External person
  • Lucas-Barbosa, D., Co-promotor
Award date16 Oct 2020
Place of PublicationWageningen
Publisher
Print ISBNs9789463954815
DOIs
Publication statusPublished - 2020

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