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Detection and Identification of Pseudomonas syringae pv. atropurpurea by PCR Amplification of Specific Fragments from an Indigenous Plasmid. Y. Takahashi, Research Institute of Japan Plant Protection Association, Ushiku, Ibaraki 300-12, Japan. T. Omura and H. Hibino, National Agriculture Research Center, Tsukuba, Ibaraki 305, Japan; and M. Sato, National Institute of Sericultural and Entomological Science, Tsukuba, Ibaraki 305, Japan. Plant Dis. 80:783-788. Accepted for publication 9 April 1996. Copyright 1996 The American Phylopathological Society. DOI: 10.1094/PD-80-0783.

A highly sensitive and specific polymerase chain reaction (PCR) method was developed to detect pCORl, a plasmid associated with pathogenicity to Italian ryegrass and synthesis of coronatine in Pseudomonas syringae pv. atropurpurea. Specific pCORl fragments were amplified from DNA extracts of P. syringae pv. atropurpurea with primers complementary to ends of fragments obtained from Pstl digestion of a 17-kb fragment, the largest from EcoRl digestion of pCORl. One hundred twenty-seven bacterial strains, including 18 strains of P. syringae pv. atropurpurea, 7 Cor- mutants of P. syringae pv. atropurpurea, 52 strains of 38 different pathovars of P. syringae, 13 nonpathogenic strains of P. syringae, and 37 strains of different bacteria species, were tested by PCR. Though DNA sequences resembling parts of the 17-kb fragment were found in some strains of different pathovars of P. syringae, all the specific fragments of pCORl were amplified only from strains of P. syringae pv. atropurpurea. The results demonstrated that the distribution of pCORl is limited to strains of P. syringae pv. atropurpurea. It is suggested that pCORl may be the pathovar-specific plasmid and moreover that the confirmation of the presence of pCORl in the strain may enable a rapid and simple identification of P. syringae pv. atropurpurea.