Separation of Strains ofPseudomonas syringaepv.tomatointo Serovars by Three Serological Methods

Abstract

Serological variation within P. syringae pv. [pathovar] tomato was observed when 26 strains from widely separated areas of the USA and Canada were tested by Ouchterlony double diffusion (ODD), microagglutination (MA) and indirect immunofluorescence (IIF) methods. A strong correlation existed between 2 of the tests for placing the strains into 2 serovars. One serovar (designated serovar I) consisted of 20 strains and serovar II contained 5 strains. One strain did not fit into either serovar. When the MA and IIF techniques were used, separation into serovars was only possible using cross absorbed antisera with other strains of P. syringae pv. tomato. ODD was not a definitive test for separation of the strains into 2 serovars. ODD was useful for identifying those strains in serovar I; inconclusive results were obtained with strains classified as serovar II. The existence of serovars should be considered in attempts to develop serological methods for rapid detection and identification of P. syringae pv. tomato.