DNA relatedness among the pathovars of Pseudomonas syringae and description of Pseudomonas tremae sp. nov. and Pseudomonas cannabina sp. nov. (ex Sutic and Dowson 1959).

A total of 48 pathovars of Pseudomonas syringae and eight related species were studied by DNA-DNA hybridization (S1 nuclease method) and ribotyping. The existence of nine discrete genomospecies was indicated. Genomospecies 1 corresponded to P. syringae sensu stricto and included P. syringae pathovars syringae, aptata, lapsa, papulans, pisi, atrofaciens, aceris, panici, dysoxyli and japonica. Genomospecies 2 included P. syringae pathovars phaseolicola, ulmi, mori, lachrymans, sesami, tabaci, morsprunorum, glycinea, ciccaronei, eriobotryae, mellea, aesculi, hibisci, myricae, photiniae and dendropanacis and nomenspecies Pseudomonas savastanoi, Pseudomonas ficuserectae, Pseudomonas meliae and Pseudomonas amygdali, which are thus synonymous. P. amygdali is the earliest valid name for this genomospecies. Genomospecies 3 included P. syringae pathovars tomato, persicae, antirrhini, maculicola, viburni, berberidis, apii, delphinii, passiflorae, philadelphi, ribicola and primulae. We recommend strain CFBP 2212 of P. syringae pv. tomato to serve as the type strain. Genomospecies 4 included 'Pseudomonas coronafaciens' and P. syringae pathovars porri, garcae, striafaciens, atropurpurea, oryzae and zizaniae and corresponds to 'P. coronafaciens'. Genomospecies 5 included P. syringae pv. tremae and corresponds to Pseudomonas tremae sp. nov. Genomospecies 6 included Pseudomonas viridiflava and the presently misidentified pathotype strains of P. syringae pv. ribicola and P. syringae pv. primulae and thus corresponds to P. viridiflava. Genomospecies 7 included P. syringae pv. tagetis and P. syringae pv. helianthi. We recommend strain CFBP 1694 of P. syringae pv. tagetis to serve as a reference strain. Genomospecies 8 included P. syringae pv. these and Pseudomonas avellanae and thus corresponds to P. avellanae. Genomospecies 9 included P. syringae pv. cannabina and corresponds to Pseudomonas cannabina sp. nov. Ribotyping (SmaI and HincII endonucleases) could separate seven of the nine genomospecies. The unnamed genomospecies 3 and 7 will be named when phenotypic data are available for identification. Two species are described, P. tremae sp. nov. and P. cannabina sp. nov. Other species will be named when phenotypic data are available for identification.