First Report of Streptomyces stelliscabiei Causing Potato Common Scab in Michigan

Potato (Solanum tuberosum L.) common scab can be caused by multiple Streptomyces spp., with S. scabies as a predominant species (2,3). However, according to our survey in August 2007, many symptomatic potato tubers did not have S. scabies in Michigan. To identify the pathogen, potato tubers with scab symptoms were collected from two fields in Michigan, and Streptomyces spp. were isolated using Streptomyces selective medium (STR) (2). Pure cultures of the isolates were obtained by transferring single colonies and incubation at 28°C on STR. Three isolates, designated HER21, HER24, and HER26, were identified as Streptomyces stelliscabiei based on morphological and physiological characterization (1). Bacterial cultures were prepared in liquid yeast malt extract at 28°C on an incubator shaker at 150 rpm. Genomic DNA was extracted from the cultures and used as a template for PCR with species-specific primers for Streptomyces spp. (4). The isolates gave a positive PCR reaction with primers Stel3 and T2st2 for S....