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Indigenous Plasmids in Pseudomonas solanacearum. Victor M. Morales, Research associate, Department of Plant Pathology, University of Wisconsin, Madison 53706; Luis Sequeira, professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 75:767-771. Accepted for publication 14 February 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-767.

Twenty-two of 39 strains of Pseudomonas solanacearum harbor one or two plasmids with relative masses that range from 5.0 to more than 500 megadaltons. When plasmid DNA from strains 85, 26, and 10 was digested with Bam HI and Eco RI, very different fragment patterns were obtained, suggesting that each replicon represents a unique plasmid. The molecular weights of these plasmids, as calculated from the restriction patterns, are 84 x 106, 93 x 106, and 120 x 106, respectively. One strain (mps5) was found to harbor two small plasmids. A restriction enzyme map of the smaller (5-megadalton) plasmid was obtained. This plasmid, pW15, may be useful in the construction of a stable cloning vector for this species. There was no apparent relationship between the presence of plasmids and host of origin, natural resistance to antibiotics, or geographic origin of the strains examined.