VIEW ARTICLE

Genetics

The Use of Transposon Mutagenesis in the Isolation of Nutritional and Virulence Mutants in Two Pathovars of Pseudomonas syringae. Dirk M. Anderson, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; Dallice Mills, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331. Phytopathology 75:104-108. Accepted for publication 9 July 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-104.

Transposon Tn5, which confers kanamycin resistance, was introduced into the genomes of Pseudomonas syringae pv. syringae PS9020 and P. syringae pv. phaseolicola PP7010 by conjugation with Escherichia coli SM10 containing the suicide plasmid vector pSUP1011. Approximately 0.5- 0.6% of over 4,000 kanamycin-resistant (Km^r) colonies that were analyzed mutated to auxotrophy. Most auxotrophs reverted at low frequencies (<10^{- 8}), and most prototrophic revertants were kanamycin-sensitive. Of approximately 2,400 Km^r colonies assayed on leaves of Phaseolus vulgaris, 0.3- 0.4% had partially or completely lost the ability to induce wild-type virulence symptoms. Blot hybridization analysis of EcoRI-digested total DNA from these strains revealed insertion of Tn5 at unique sites. The identification of avirulent mutants that resulted from transposition of Tn5 provides a mechanism for cloning and characterizing virulence determinants in these strains.