A Patchwork of Streptomyces Species Isolated from Potato Common Scab Lesions in North America

To determine distribution and prevalence of Streptomyces species associated with common scab in North America, more than 1,400 isolates were made from scabby potato tubers. Samples were obtained from locations across the continent, and from multiple sites in close geographic proximity. Most potentially pathogenic isolates belonged to four species previously associated with common scab, S. scabies, S. europaeiscabiei, S. stelliscabiei, and S. sp. IdahoX. Additionally, small numbers of potentially pathogenic isolates were identified as S. acidiscabies, S. turgidiscabies and six additional ribotypes. S. europaeiscabiei was most common in the west and S. scabies predominated in the middle and eastern Midwest. Beyond this geographic trend, species distribution was patchy. A single species often predominated in a field while neighboring fields had different species. Local and regional variation was seen when isolates were genotyped for repetitive sequence element patterns, reflecting the conserved or core genome, and genes characteristic of the Streptomyces pathogenicity island, reflecting flexible components of the Streptomyces genome. This is the largest survey to date of the distribution of common scab-causing species, and will be a resource for population biology studies and for tracing the evolutionary history and spread of common scab-associated Streptomyces.