Isozyme analysis for the identification of Pseudomonassyringae pathovar pisi strains

Abstract

Distinction between Pseudomonas syringae pathovar (pv.) pisi (Ps. syr. pisi), responsible for bacterial blight of pea (Pisum sativum), and pv. syringae (Ps. syr. syringae), still requires strain inoculation onto peas. Patterns of enzymes including esterase (EST) and superoxide dismutase (SOD) were examined for diagnostic purposes. Profiles of 59 Ps. syr. pisi strains and 53 Ps. syr. syringae strains were compared. Pseudomonas syringae pisi was characterized by one unique zymotype for SOD and two slightly different zymotypes for EST. Pseudomonas syringae syringae zymotypes were very heterogeneous with 10 different zymotypes for SOD and 32 for EST. Twenty-four percent of the Ps. syr. syringae strains 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 patterns were correlated to race structure of the pathovar, zymotype 1 corresponding to races 2, 3, 4 and 6, and zymotype 2 to races 1, 5 and 7. Esterase isozyme profiling was proposed as a new identification procedure for bacterial pea blight agent.