VIEW ARTICLE

Special Topics

Isolation and Characterization of Phages Useful for Identifying Pseudomonas syringae pv. tomato. D. A. Cuppels, Assistant plant pathologist, Research Centre, Agriculture Canada, University Sub Post Office, London, Ontario N6A 5B7; Phytopathology 73:1376-1381. Accepted for publication 6 April 1983. Copyright 1983, Department of Agriculture, Government of Canada. DOI: 10.1094/Phyto-73-1376.

Sixteen phages were isolated from tomato field soil and plant debris with six Pseudomonas syringae pv. tomato strains as the propagating hosts. Fifty-five strains of P. syringae pv. tomato and 51 strains from other pathovars of P. syringae were tested for lytic responses to these phages. Phage sensitivity patterns did not change with time or after passage through tomato plants. Four of the phages, PT1, PT18, PT20, and PT32 had a high degree of specificity for P. syringae pv. tomato. PT32, for example, lysed 90% of the virulent P. syringae pv. tomato strains tested, but less than 4% of the strains from other pathovars of P. syringae. None of the isolates of P. syringae pv. syringae from tomato and less than half of the avirulent strains of P. syringae pv. tomato tested were lysed by these phages. Phages PT1 and PT18, which have isometric heads and long, striated, noncontractile tails, were members of morphological group B1. Phages PT20 and PT32, which have isometric heads and short, noncontractile tails, were members of morphological group C1. When used in combination with selected physiological characters (d(- ) tartrate, erythritol, and dl-lactate utilization and polypectate degradation), phage sensitivity patterns clearly distinguished virulent strains of P. syringae pv. tomato from the other pathovars of P. syringae that were tested.