Potential transmission pathways of two bacteria associated with acute oak decline Brenneria Goodwinii and Gibsiella Quercinecans

Bonham, E. (2021) Potential transmission pathways of two bacteria associated with acute oak decline Brenneria Goodwinii and Gibsiella Quercinecans. Doctoral thesis, Harper Adams University.

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Acute Oak Decline (AOD) is a tree health condition affecting two oak species in Britain Quercus robur and Q.petraea. Symptomatic trees develop vertical fissures with associated stem bleeding due to tissue necrosis. Two newly identified bacteria species Brenneria goodwinii and Gibbsiella quercinecans have been isolated from this exudate and are now thought to contribute to the inducement of stem bleeding. Genetic analysis has indicated both bacteria have the capacity to be pathogenic and are able break down plant tissue. How these bacteria colonise oak and any potential movement pathways allowing the spread of the bacteria within and between trees remains unknown. The association of Brenneria goodwinii and Gibbsiella quercinecans with the oak phyllosphere was first considered. Two primary pathways were then identified and explored. These were movement via insect vectors and airborne movement via rain water. A number of different techniques were used to establish whether any of these pathways had potential as colonisation routes. Stem lesions focus the collection on wood boring beetles as potential insect vectors and this will include A.biguttatus due to its associated distribution with symptomatic sites although as discussed there is limited evidence to support this. The presence of stem lesions and tissue necrosis symptomatic of Acute Oak Decline has led to suggestions a xylophagous (wood boring) insect may be involved. Other wood boring insects such as those with xylophagous and saproxylic lifestyles also utilise oak as a host and have potential to act as passive or active vectors as well. The second mechanism to be investigated will be the potential for airborne movement via rain to move bacteria within and between oak hosts. Results indicate that Brenneria goodwinii and Gibbsiella quercinecans are associated with live oak leaves, leaf litter, acorns and catkins. Investigations suggest that both are part of the oak bacterial community and hint at differences in lifestyles between Brenneria goodwinii and Gibbsiella quercinecans. In addition the results suggest that both bacteria potentially have multiple means of encountering new hosts.

Item Type: Thesis (Doctoral)
Divisions: Agriculture and Environment (from 1.08.20)
Depositing User: Ms Kath Osborn
Date Deposited: 12 Aug 2021 15:00
Last Modified: 12 Aug 2021 15:00
URI: https://hau.repository.guildhe.ac.uk/id/eprint/17731

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