Diversity within the novel Dickeya fangzhongdai sp., isolated from infected orchids, water and pears

Abstract

Members of the genus Dickeya are plant pathogens that mostly cause soft-rot diseases. Diversity within the genus has led to the recent description of three novel species (i.e. a mainly clonal D. solani of economic consequence in potatoes, D. aquatica from water samples and D. fangzhongdai isolated from necrotic pear trees in China). However, multilocus sequence analysis (MLSA) has highlighted the occurrence of seven isolates not related to the defined Dickeya species. These include a previously unclassified group of Dickeya strains isolated from monocotyledonous plants, Dickeya sp. S1, Dickeya sp. B16, and Dickeya sp. NCPPB 3274, as well as Dickeya sp. MK7, a strain isolated from water, and misassigned strains D. solani ND14, D. solani M005 and D. chrysanthemi M074. Here, it is reported that these isolates can be classified as D. fangzhongdai by using average nucleotide identity analysis and MLSA. However, variations in phenotypic characterization featuring colony morphology and carbon utilization assays revealed a diversity of bacterial isolates classified as D. fangzhongdai. Based on the results of the genomic analysis, the classification of Dickeya sp. S1, Dickeya sp. B16, Dickeya sp. MK7, Dickeya sp. NCPPB 3274 to D. fangzhongdai is proposed as well as the reclassification of D. solani ND14, D. solani M005 and D. chrysanthemi M074 to D. fangzhongdai.