Evaluation of determinative tests for pathovars of Pseudomonas syringae van Hall 1902

The utility of 36 presumptive determinative tests for 32 pathovars of Pseudomonas syringae was investigated. A total of 395 strains was examined. Most strains of 12 of these pathovars (Ps. syringae pv. cannabina, Ps. syr. delphinii, Ps. syr. glycinea, Ps. syr. helianthi, Ps. syr. lachrymans, Ps. syr. mori, Ps. syr. morsprunorum, Ps. syr. phaseolicola, Ps. syr. 'porri', Ps. syr. papulans, Ps. syr. savastanoi and Ps. syr. tabaci) formed clusters when test data were compared by centroid analysis. Pseudomonas syr. syringae, Ps. syr. aptata, Ps. syr. atrofaciens, Ps. syr. dysoxyli and Ps. syr. japonica formed a single cluster, indicating their possible synonymy. Strains of Ps. syr. antirrhini and Ps. syr. tomato were indistinguishable, as were those of Ps. syr. garcae and Ps. syr. oryzae. Strains of Ps. syr. berberidis, Ps. syr. coronafaciens, Ps. syr. eriobotryae, Ps. syr. maculicola, Ps. syr. passiflorae, Ps. syr. pisi and Ps. syr. striafaciens and Ps. syr. tagetis did not form distinguishable clusters. The tests which reliably differentiated pathovars are recorded in a determinative scheme.