DNA relatedness among strains of Streptomyces pathogenic to potato in France: description of three new species, S-europaeiscabiei sp nov, and S-stelliscabiei sp. nov associated with common scab, and S-reticuliscabiei sp nov associated with netted scab

The genomic relatedness was evaluated by DNA-DNA hybridization for 23 strai ns (21 were pathogenic and two were saprophytic strains) isolated from lesi ons of common and netted scab in France and 19 strains from other countries , including type strains of Streptomyces species. Three genomospecies were defined within the conventional species of Streptomyces scabies, and these genomospecies were different from other pathogenic described species (Strep tomyces acidiscabies, Streptomyces caviscabies) based on previously publish ed phenotypic data. Two of these genomospecies (1 and 3) correspond to new species, for which the names Streptomyces europaeiscabiei sp. nov. (with ty pe strain CFBP 4497(T)) and Streptomyces stelliscabiei sp. nov. (with type strain CFBP 4521(T)) are proposed. Genomospecies 2 corresponds to S. scabie s (with type strain CFBP 4517(T) = ATCC 49173(T)), and includes only one Fr ench strain. The pathogenic strains associated with netted scab lesions con stituted a new species that was named Streptomyces reticuliscabiei sp. nov. (with type strain CFBP 4531(T)). The G+C content of DNA from the three str ains CFBP 4497(T) (S. europaeiscabiei), CFBP 4521(T) (S. stelliscabiei), CF BP 4531(T) (S. reticuliscabiei) was 71.3, 71.0 and 69.8 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences showed that the typ e strain CFBP 4497(T) was very similar to the type strain of S. scabies, wh ereas, the type strain of S. stelliscabiei, CFBP 4521(T), was very similar to the type strain of Streptomyces bottropensis. On the basis of 16S rRNA g ene sequences, the type strain of S. reticuliscabiei, CFBP 4531(T), differe d extensively from the other strains of Streptomyces tested.