Brenneria goodwinii and Gibbsiella quercinecans isolated from weeping cankers on Quercus robur L. in Spain

Abstract

In Asturias, northern region of Spain, pedunculate oak (Quercus robur L.) with symptoms of disease such as cracks in the bark with dark exudates, was observed in June 2017. Two different bacteria were isolated from the recovered sample. The two bacteria were biochemically very similar and so were identified by 16S rDNA sequences. The sequence of strain LPPA 3463 had 99% similarity with that of the type strain of the species Brenneria goodwinii Denman et al., and the sequence of strain LPPA 3461 showed the same result with respect to the sequence of the type strain of the species Gibbsiella quercinecans Brady et al. For more accurate identification, gyrB and atpD genes were also sequenced. Pathogenicity tests were initially carried out by puncture with the two bacteria on acorns and after 15 days, a rotten area was observed in the nuts while the controls, inoculated with sterile water, remained healthy. B. goodwinii and G. quercinecans have been consistently associated with Acute Oak Disease (AOD) affecting native oak trees in the UK, usually with presence of galleries produced by the buprestid beetle Agrilus. However, larval galleries of the Agrilus were not present in the pedunculate oak sample. G. quercinecans was reported in Spain on both Quercus ilex L. (holm oak) and Q. pyrenaica Willd. (pyrenean oak), but not on Q. robur. The bacterium B. goodwinii has not been described in Spain, and consequently this is the first report of these bacteria in pedunculate oak in Spain.