Asamoah, Samuel
(2024)
Role of cereal aphid in the epidemiology of Fusarium head blight in wheat.
PhD thesis, University of Nottingham.
Abstract
Cereal aphids can play a significant role in the epidemiology of Fusarium head blight (FHB) by amplifying the reduction of the physiological and biochemical fitness of the host plant. However, little work has been done regarding the systemic effects of aphid feeding on the host and the compatibility of different aphid species with Fusarium graminearum for dispersal and pathogenesis. Therefore, the primary aim of the work presented in this thesis was to determine the ecological and epidemiological consequences of interactions between two different species of cereal aphids, Rhopalosiphum padi and Sitobion avenae and F.graminearum. This work investigated the aphids' pre- and post-alighting behavioural responses to Fusarium graminearum-infected wheat cultivars with contrasting disease resistance profiles. Results showed that alate R. padi was attracted to both FHB susceptible and resistant plants infected with DON-producing F. graminearum while S. avenae was repelled. One of the mechanisms of R.padi attraction was the release of distinct volatile emissions from FHB-infected hosts. However, sharing the host space with the pathogen resulted in the competitive exclusion of both aphids by F. graminearum because aphid fitness was reduced, as shown by decreased pest reproductive rates and increased mortality. In contrast, aphid activity on the shared ear niche resulted in enhanced pathogen fitness because disease severity and Fusarium mycotoxins, such as DON, substantially increased in both genotypes.
Differences in ecological niche adaptations of the aphids were implicated in contrasting outcomes of aphid-fusarium interactions. Thus, the ear-adapted S. avenae was more susceptible to adverse changes in the host environment induced by the pathogen. In contrast, R. padi preferentially settled on wheat leaves of plants infected with Fusarium graminearum, thus actively avoiding direct interactions with the pathogen on the ear. Both FHB susceptible (cv. Gallant) and resistance (cv. Sumai 3) cultivars accumulated more mycotoxins and showed acceleration of FHB disease development when subjected to aphids and DON-producing F. graminearium co-habitation. However, co-operative relationships were formed between a DON producer and R. padi when the pest and pathogen occupied spatially separated niches on their shared host. In contrast a DON producing F. graminearum antagonised S. avenae when feeding both locally and distally on co-habited plants. The observed co-operation between R. padi and the DON producer resulted in increased pest infestation on the hosts, suggesting some pest-pathogen compatibility and potentially co-adaptation strategy deployed by the pest.
Finally, it was shown that indirect interactions on the shared host niche, S. avenae, formed mutualistic relationships with NIV-producing F. graminearum, realising benefits for the pest-pathogen complex with important consequences for pathogen dispersal. Attractive volatile organic compounds caused by the NIV chemotype of F. graminearum played a role in recruiting S. avenae for successful pathogen transmission. Transmission from diseased to a healthy host was achieved by alate aphids with increased reproductive success when feeding on plants infected by a NIV producer.
The results from this thesis have significant implications for FHB epidemiology. The findings show that different mycotoxin producers and aphid species have the capacity to form co-adapted pest-pathogen complexes on the host with synergistic consequences for FHB disease, mycotoxins, and pest infestations. This suggests the potential for further research to elucidate the mechanisms of assembly of these complexes and the molecular basis of host defence suppression. In addition, field experiments will be needed to quantify wheat losses due to these pest-pathogen complexes and identify the best management strategies for integrated pest and disease management. The anticipation of these future developments is palpable, and the potential impact of this research is significant.
| Item Type: |
Thesis (University of Nottingham only)
(PhD)
|
| Supervisors: |
Ray, Ruminana
Dong-Hyun, Kim |
| Keywords: |
Fusarium graminearum, aphids, transmission studies aphids, S.avenae, R.padi |
| Subjects: |
Q Science > QL Zoology |
| Faculties/Schools: |
UK Campuses > Faculty of Science > School of Biosciences |
| Item ID: |
79607 |
| Depositing User: |
Asamoah, Samuel
|
| Date Deposited: |
13 Dec 2024 04:40 |
| Last Modified: |
13 Dec 2024 04:40 |
| URI: |
https://eprints.nottingham.ac.uk/id/eprint/79607 |
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