A collection of 75 strains of Pectobacterium chrysanthemi (including all biovars and pathovars) and the type strains of Brenneria paradisiaca (CFBP 4178T) and Pectobacterium cypripedii (CFBP 3613T) were studied by DNA–DNA hybridization, numerical taxonomy of 121 phenotypic characteristics, serology and 16S rRNA gene-based phylogenetic analyses. From analysis of 16S rRNA gene sequences, it was deduced that P. chrysanthemi strains and B. paradisiaca CFBP 4178T formed a clade distinct from the genera Pectobacterium and Brenneria; therefore, it is proposed to transfer all the strains to a novel genus, Dickeya gen. nov. By DNA–DNA hybridization, the strains of P. chrysanthemi were distributed among six genomic species: genomospecies 1 harbouring 16 strains of biovar 3 and four strains of biovar 8, genomospecies 2 harbouring 16 strains of biovar 3, genomospecies 3 harbouring two strains of biovar 6 and five strains of biovar 5, genomospecies 4 harbouring five strains of biovar 2, genomospecies 5 harbouring six strains of biovar 1, four strains of biovar 7 and five strains of biovar 9 and genomospecies 6 harbouring five strains of biovar 4 and B. paradisiaca CFBP 4178T. Two strains of biovar 3 remained unclustered. Biochemical criteria, deduced from a numerical taxonomic study of phenotypic characteristics, and serological reactions allowed discrimination of the strains belonging to the six genomic species. Thus, it is proposed that the strains clustered in these six genomic species be assigned to the species Dickeya zeae sp. nov. (type strain CFBP 2052T=NCPPB 2538T), Dickeya dadantii sp. nov. (type strain CFBP 1269T=NCPPB 898T), Dickeya chrysanthemi comb. nov. (subdivided into two biovars, bv. chrysanthemi and bv. parthenii), Dickeya dieffenbachiae sp. nov. (type strain CFBP 2051T=NCPPB 2976T), Dickeya dianthicola sp. nov. (type strain CFBP 1200T=NCPPB 453T) and Dickeya paradisiaca comb. nov., respectively.

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