ISOZYME ANALYSIS FOR THE IDENTIFICATION OF PSEUDOMONAS-SYRINGAE PATHOVAR PISI STRAINS

Distinction between Pseudomonas syringae pathovar (pv.) pisi (Ps. syr. pisi), responsible for bacterial blight of pea (Pisum sativum), and P V syringae (Ps. syr. syringae), still requires strain inoculation onto peas. Patterns of enzymes including esterase (EST) and superoxide dis mutase (SOD) were examined for diagnostic purposes. Profiles of 59 Ps. syr. pisi strains and 53 Ps. syr. syringae strains were compared. Pse udomonas syringae pisi was characterized by one unique zymotype for SO D and two slightly different zymotypes for EST. Pseudomonas syringae s yringae zymotypes were very heterogeneous with 10 different zymotypes for SOD and 32 for EST. Twenty-four percent of the Ps. syr. syringae s trains shared SOD zymotype 1 of Ps. syr. pisi, thus preventing the use of this enzymatic system for identification. In contrast, the two EST zymotypes of Ps. syr. pisi strains were specific to the pathovar and could be used for its identification. The two Ps. syr. pisi EST patter ns were correlated to race structure of the pathovar, zymotype 1 corre sponding to races 2, 3, 4 and 6, and zymotype 2 to races 1, 5 and 7. E sterase isozyme profiling was proposed as a new identification procedu re for bacterial pea blight agent.