Recent studies on acute oak decline, involving Brenneria goodwinii and other bacteria
Brenneria goodwinii was first described in the United Kingdom in association with symptoms of acute oak decline. Symptoms are characterized by bark cracks, bleeding cankers, tree decline and mortality within 4 to 6 years after the onset of the first symptoms. This disease syndrome also involves other bacteria, such as Gibbsiella quercinecans and Rahnella victoriana, and possibly the co-occurrence of insects (e.g. Agrilus biguttatus). Following its initial description in the United Kingdom, B. goodwinii has been reported from other countries on several oak species, often with other bacterial species and in association with symptoms of acute oak decline.
In Iran, acute oak decline has been observed in the Hyrcanian forest (Mazandaran and Golestan provinces). Laboratory tests confirmed the presence of B. goodwinii, as well as other bacteria (B. roseae subsp. roseae, Brenneria sp., B. nigrifluens and Gibbsiella sp.) (Bakhshi Ganje et al., 2020).
In Latvia, B. goodwinii and G. quercinecans were detected for the first time in 2018 in several forest sites on pedunculate oak trees (Quercus robur) (EPPO RS 2018/126).
In Poland, 7 samples were collected in 2019 from declining pedunculate oak trees (Quercus robur) in the Chojnów Forest District (Southwestern Poland). Molecular tests revealed the presence of B. goodwinii and G. quercinecans in 2 samples (Tkaczyk et al., 2021)
In Portugal, acute oak decline was observed in March 2018 in a Quercus suber forest in Alcácer (Alentejo). Dead trees showed brownish leaves, bleeding on the outer surface of the bark, necrotic lesions in the inner bark and signs of larval activity of the ambrosia beetle Platypus cylindrus. Laboratory tests (PCR, sequencing) revealed the presence of B. goodwinii. Inoculation tests confirmed the pathogenicity of B. goodwinii on Q. suber plantlets and Koch postulates were completed (Fernandes et al., 2022).
In Spain, B. goodwinii and G. quercinecans were observed in June 2017 on pedunculate oak trees (Quercus robur) in Asturias. G. quercinecans had previously been reported on Q. ilex and Q. pyrenaica, but not on Q. robur. This was also the first record of B. goodwinii in Spain (González et al., 2022).
In Switzerland, B. goodwinii, G. quercinecans and R. victoriana were detected for the first time in 2017 in the municipality of Muttenz (Basel-Stadt canton) on sessile oaks (Quercus petraea) (EPPO RS 2018/104).
Sources
Bakhshi Ganje M, Shams-Bakhsh M, Mackay J, Rahimian H (2020) Identification and characterization of bacterial strains associated with diseased oak trees in Northern Iran. Forest Pathology 50, e12571. https://doi.org/10.1111/efp.12571
Fernandes C, Duarte L, Naves P, Sousa E, Cruz L (2022) First report of Brenneria goodwinii causing acute oak decline on Quercus suber in Portugal. Journal of Plant Pathology 104, 837–838. https://doi.org/10.1007/s42161-022-01046-w
González AJ, Ciordia M (2020) Brenneria goodwinii and Gibbsiella quercinecans isolated from weeping cankers on Quercus robur L. in Spain. European Journal of Plant Pathology 156, 965–969. https://doi.org/10.1007/s10658-019-01891-z
Tkaczyk M, Celma L, Ruņģis DE, Bokuma G (2021) First report of Brenneria goodwinii and Gibbsiella quercinecans bacteria, detected on weaken oak trees in Poland. Baltic Forestry 27(1), 563. https://doi.org/10.46490/BF563