Proposal to reclassify Brenneria quercina (Hildebrand and Schroth 1967) Hauben et al. 1999 into a new genus, Lonsdalea gen. nov., as Lonsdalea quercina comb. nov., descriptions of Lonsdalea quercina subsp. quercina comb. nov., Lonsdalea quercina subsp. iberica subsp. nov. and Lonsdalea quercina subsp. britannica subsp. nov., emendation of the description of the genus Brenneria, reclassi- fication of Dickeya dieffenbachiae as Dickeya dadantii subsp. dieffenbachiae comb. nov., and emendation of the description of Dickeya dadantii Carrie L. Brady, 1 Ilse Cleenwerck, 1 Sandra Denman, 2 Stephanus N. Venter, 3 Pablo Rodrı ´guez-Palenzuela, 4 Teresa A. Coutinho 3 and Paul De Vos 1 Correspondence Teresa A. Coutinho teresa.coutinho@fabi.up.ac.za 1 BCCM/LMG Bacteria Collection, Ghent University, K. L. Ledeganckstraat 35, B-9000 Ghent, Belgium 2 Forest Research, Centre for Forestry and Climate Change, Alice Holt Lodge, Farnham, Surrey GU10 4LH, UK 3 Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa 4 Centro de Biotecnologı ´a y Geno ´ mica de Plantas UPM-INIA, Campus de Montegancedo, Autovı ´a M-40 Km 38, 28223 Pozuelo de Alarco ´ n, Madrid, Spain Bacterial isolates from oak trees in Spain and Britain, showing symptoms of bark canker and Acute Oak Decline (AOD), respectively, were examined by a polyphasic approach. Both 16S rRNA gene sequencing and multilocus sequence analysis (MLSA), based on partial sequences of gyrB, rpoB, infB and atpD genes, revealed that the isolates were separated into two genetic groups according to their origin. Their closest phylogenetic relative was Brenneria quercina, the causal agent of drippy nut disease of oak, which clustered distant to the other species of the genus Brenneria. MLSA data for species of the genera Brenneria, Pectobacterium, Dickeya, Erwinia, Pantoea and Samsonia confirmed the polyphyletic nature of the genus Brenneria and indicated synonymy of Dickeya dadantii and Dickeya dieffenbachiae. DNA–DNA hybridization experiments confirmed this synonymy and also revealed DNA– DNA relatedness values of 58–73 % between the new oak isolates and B. quercina. Phenotypic and/or chemotaxonomic methods allowed B. quercina and the two genetic groups of new oak isolates to be discriminated from other recognized species of the genus Brenneria and from members of the closely related genera Dickeya, Pectobacterium and Samsonia. Based on the data obtained, the following taxonomic proposals are made: (1) reclassification of B. quercina as the type species of a novel genus, Lonsdalea gen. nov., as Lonsdalea quercina comb. nov. (type strain LMG 2724 T 5ATCC 29281 T 5CCUG 48867 T 5CFBP 3617 T 5CIP 105201 T 5DSM 4561 T 5ICMP 1845 T ), (2) classification of the oak isolates as Lonsdalea quercina subsp. iberica subsp. nov. (type strain LMG Abbreviations: AOD, acute oak decline; MLSA, multilocus sequence analysis. The GenBank/EMBL/DDBJ accession numbers for the sequences determined in this study are: JF311438–JF311446 (16S rRNA), JF311447– JF311559 (atpD), JF311560–JF311672 (gyrB), JF311673–JF311785 (infB) and JF311786–JF311897 (rpoB) as detailed in Table S1. A supplementary table and a supplementary figure are available with the online version of this paper. International Journal of Systematic and Evolutionary Microbiology (2012), 62, 1592–1602 DOI 10.1099/ijs.0.035055-0 1592 035055 G 2012 IUMS Printed in Great Britain