Genetic Diversity of Pseudomonas solanacearum: Detection of Restriction Fragment Length Polymorphisms with DNA Probes That Specify Virulence and the Hypersensitive Response. Douglas Cook. Department of Plant Pathology, University of Wisconsin, Madison 53706 U.S.A. Elizabeth Barlow, and Luis Sequeira. Department of Plant Pathology, University of Wisconsin, Madison 53706 U.S.A. . MPMI 2:113-121. Accepted 31 January 1989. This article is in the public domatin and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989.

Restriction fragment length polymorphism (RFLP) analysis involving nine DNA probes, seven of which encode information required for virulence and the hypersensitive response (HR), was used to study the relationships among 62 strains of Pseudomonas solanacearum, representing three races and five biovars. When Southern blots of EcoRI- or EcoRI and BamHI-digested genomic DNA were probed with the nine unique EcoRI cloned fragments from strains K60 or K2R, 28 distinct RFLP patterns were identified. Similarity coefficients revealed two major divisions: division I contains all members of race 1 biovars 3, 4, and 5; division II contains all members of race 1 biovar 1 and races 2 and 3. Similarity coefficients within divisions I and II are 78% ?? 9% and 62% ? 19%, respectively. In contrast, the similarity coefficient between the two divisions is only 13.5%. Division II is composed of five distinct subdivisions corresponding to race 1 biovar 1, race 3, and three subdivisions of race 2. Some subdivisions correspond to strains with distinct host ranges or geographical origins.