Transfer of Pectobacterium chrysanthemi (Burkholder et al. 1953) Brenner et al. 1973 and Brenneria paradisiaca to the genus Dickeya gen. nov. as Dickeya chrysanthemi comb. nov. and Dickeya paradisiaca comb. nov. and delineation of four novel species, Dickeya dadantii sp. nov., Dickeya dianthicola sp. nov., Dickeya dieffenbachiae sp. nov. and Dickeya zeae sp. nov.

Abstract

A collection of 75 strains of Pectobacterium chrysanthemi (including all biovars and pathovars) and the type strains of Brenneria paradisiaca (CFBP 4178(T)) and Pectobacterium cypripedii (CFBP 3613(T)) 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 4178(T) 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 4178(T). 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 2052(T)=NCPPB 2538(T)), Dickeya dadantii sp. nov. (type strain CFBP 1269(T)=NCPPB 898(T)), Dickeya chrysanthemi comb. nov. (subdivided into two biovars, bv. chrysanthemi and bv. parthenii), Dickeya dieffenbachiae sp. nov. (type strain CFBP 2051(T)=NCPPB 2976(T)), Dickeya dianthicola sp. nov. (type strain CFBP 1200(T)=NCPPB 453(T)) and Dickeya paradisiaca comb. nov., respectively.