Herbivore-Plant-Soil microbe interactions: who is helping whom

Plants interact with their environment and undergo phenotypic changes during biotic interactions with insects/pathogens. Responses to biotic stress factors are wide-ranging and can occur both above- and belowground, systematically affecting the whole plant and surrounding plant environment (phyllosphere/rhizosphere). One of the most important responses to insect herbivore colonization is the modification of external chemical signals released, which can impact on herbivore biology by recruitment of herbivore natural enemies, and by signalling to neighbouring plants. Furthermore, herbivores with different feeding modes can induce different chemical signalling pathways. The release of these compounds belowground can affect plant interactions with soil microbial communities that are associated with the plant root system. The composition of the soil microbial community has been recognized as an important factor in plant health. The accumulation of beneficial organisms such as nitrogen-fixing bacteria or mycorrhizal fungi for instance can improve plant performance, while the accumulation of pathogens can suppress plant growth.
In the project, we hypothesize that:
(1) Aboveground herbivore attack will change the chemistry belowground through modifications of exudates released into the soil environment.
(2) This modification to exudates will influence the plant microbiome affecting plant-microbe as well as microbe-microbe interactions.
The consequences of insect herbivore-plant-soil microbe interactions are vital to improving crop productivity through understanding of the signalling chemistry belowground leading to new interventions on suppression of insect and pathogen pests.
Therefore, this PhD aims to address the following questions:
1. How do different modes of aboveground insect pest damage (sucking, chewing) impact upon the rhizosphere microbiome?
2. How do microbial communities interact with plant root exudates containing small lipophilic molecule chemical signals?
3. Do root exudates lead to long-lasting changes in the rhizosphere which could affect microbial/plant succession?

To address these three aims detailed above, the following programme of research will be carried out by the student, based around 3 objectives:
1. 1 Characterise how chemical compounds released into the rhizosphere (volatile and non-volatile) through the wheat root system change under two different herbivore feeding modes (sap-sucking and leaf-chewing).
2. Investigate how exudates interact with rhizosphere microbial communities before and after pest attack.
3. Investigate the impact on the plant system by the modification of chemistry belowground.