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 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.

Assessment of recent outbreaks of Dickeya sp. (syn. Erwinia chrysanthemi) slow wilt in potato crops in Israel

“…According to Samson et al (2005), all biovar 3 strains cluster into D. zeae and D. dadantii, but this new group does not fit in one of these genomic species and may be a new one (unpublished results); therefore, the new strains are referred to as Dickeya sp. biovar 3 strains.…”

“…This biovar was only found previously in blackleg-diseased plants in high temperature regions, such as Australia and some parts of Peru (Cother 1980;De Lindo et al 1978). So far all biovar 1 and 7 strains are grouped into D. dianthicola according to the publication of Samson et al (2005) and our own results using genetic techniques to group these strains. However, for biovar 3 it is more complicated.…”

“…The important Dickeya spp. causing disease on potato are (biovar 3) strains of D. dadantii and D. zeae, which are pathogens of potato in warm climates, and the more temperate-adapted (biovar 1and 7) strains of D. dianthicola that appear to be spreading on potato in Europe (Samson et al 2005). Disease symptoms are variable, including pre-emergence tuber decay in semi-arid areas (Cother 1980), extensive stem rotting in tropical areas (de Lindo et al 1978), wilt associated with limited stem rot in cool-temperate regions (Tanii and Baba 1971), and wilt without stem rot in Israel (Lumb et al 1986).…”

“…The new classification distinguishes the Dickeya spp. from the other potato soft rot Erwinia carotovora spp., recently classified into the genus Pectobacterium (Samson et al 2005). Dickeya spp.…”

Biochemical and genetical analysis reveal a new clade of biovar 3 Dickeya spp. strains isolated from potato in Europe

“…(Samson et al 2005), formerly named Pectobacterium chrysanthemi (Hauben et al 1998) and Erwinia chrysanthemi (Burkholder et al 1953) are the causal agents of stem wet rot and blackleg in potato. These bacteria can also cause soft rot during transit and storage.…”