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 strains (21 were pathogenic and two were saprophytic strains) isolated from lesions 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 (Streptomyces acidiscabies, Streptomyces caviscabies) based on previously published phenotypic data. Two of these genomospecies (1 and 3) correspond to new species, for which the names Streptomyces europaeiscabiei sp. nov. (with type strain CFBP 4497T) and Streptomyces stelliscabiei sp. nov. (with type strain CFBP 4521T) are proposed. Genomospecies 2 corresponds to S. scabies (with type strain CFBP 4517T = ATCC 49173T), and includes only one French strain. The pathogenic strains associated with netted scab lesions constituted a new species that was named Streptomyces reticuliscabiei sp. nov. (with type strain CFBP 4531T). The G+C content of DNA from the three strains CFBP 4497T (S. europaeiscabiei), CFBP 4521T (S. stelliscabiei), CFBP 4531T (S. reticuliscabiei) was 71.3, 71.0 and 69.8 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences showed that the type strain CFBP 4497T was very similar to the type strain of S. scabies, whereas, the type strain of S. stelliscabiei, CFBP 4521T, was very similar to the type strain of Streptomyces bottropensis. On the basis of 16S rRNA gene sequences, the type strain of S. reticuliscabiei, CFBP 4531T, differed extensively from the other strains of Streptomyces tested.