First report of Brenneria goodwinii, Gibbsiella quercinecans and Rahnella victoriana in declining oaks in France

Eichenlaub, L.; Eichenlaub, Lisa; Denman, S.; Denman, Sandra; Brady, C.; Maddock, D.; Maddock, Daniel; Robledo‐Garcia, F.; Robledo-Garcia, F.; Aubert, A.; Husson, C.; Robin, C.; Robin, Cecile

Abstract

Acute Oak Decline, Quercus petraea, Quercus robur Acute Oak Decline (AOD) is mediated by abiotic factors (temperature and precipitation) and triggered by insects (mainly the bark-boring beetle Agrilus biguttatus) and a complex of bacterial species (mainly Bren-neria goodwinii, Gibbsiella quercinecans and Rahnella victoriana) (Denman et al., 2017; Doonan et al., 2020). Given the extent of oak dieback and the prevalence of A. biguttatus in France (Saintonge & Goudet, 2020; Sallé et al., 2022), a preliminary study was done in five French forests to assess the prevalence of AOD symptoms (bleeding cortical lesions on the trunk associated with insect emergence holes and dieback) and to determine the bacteria associated with those symptoms. The mean prevalence of AOD symptoms was estimated at 37% arround 20 trees assessed in each of the five forests. Bark samples and, when possible, exudates were taken from lesions associated with insect emergence holes and/or cracks (Fig. 1). Bacterial isolations were made from 43 bark samples and 11 exudate samples by plating on three agar media (Luria, Gifu Anaerobic and Eosin Methylene Blue) and incubated at 22 • C for one to five days. Bacterial strains were identified by high-resolution melting (Brady et al., 2016) or 16S rRNA sequencing (Denman et al., 2016). The sequenced strains had 100% identity with sequences of reference strains (GenBank Accession Nos. CP014137.1, CP014136.1 and NR_146847.1). The percentage of trees infected with G. quercinecans, B. goodwinii and R. victoriana was 21, 16 and 12, respectively. These AOD-associated bacteria were detected with a higher success rate in exudates (81%) than in bark (25%). Gibbsiella quercinecans and B. good-This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

• Journal Article Type: Article
• Acceptance Date: Mar 13, 2024
• Online Publication Date: Mar 26, 2024
• Publication Date: Apr 30, 2024
• Deposit Date: Mar 27, 2024
• Publicly Available Date: Apr 4, 2024
• Journal: New Disease Reports
• Print ISSN: 2044-0588
• Electronic ISSN: 2044-0588
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 49
• Issue: 2
• Article Number: e12264
• DOI: https://doi.org/10.1002/ndr2.12264
• Keywords: Quercus robur, Acute Oak Decline, Quercus petraea
• Public URL: https://uwe-repository.worktribe.com/output/11846759