Abstract
Taxonomic studies were made on Streptomyces species, causal organisms of potato common scab, isolated from lesions of potato tubers and sugar beet roots in Japan. They were divided into two groups based on the spore chain morphology: spiral spore chain isolates (SI) group and rectiflexible spore chain isolates (RFI) one. Although the two groups did not significanlty differ each other in their physiological and biochemical characteristics, DNA homology study further divided them into four distinct groups: SI from potato, RFI from potato, SI from sugar beet, and RFI from sugar beet. Because of the low DNA homology values among the four groups, they should be considered as separate species. Present study confirm that the potato common scab is caused by at least four genetically distinct species of Streptomyces.
