ASSESSMENT OF GENETIC DIVERSITY AMONG STRAINS OF PSEUDOMONAS-SYRINGAEBY PCR-RESTRICTION FRAGMENT LENGTH POLYMORPHISM ANALYSIS OF RIBOSOMAL-RNA OPERONS WITH SPECIAL EMPHASIS ON P-SYRINGAE PV TOMATO

Phylogenetic relationships among 77 bacterial strains belonging to Pse udomonas syringae and Pseudomonas viridiflava species were assessed by analysis of the PCR-restriction fragment length polymorphism (RFLP) p atterns of three DNA fragments corresponding to rrs and rrl genes and the internal transcribed spacer, ITS1. No difference among all strains in rrs and rrl genes was observed with 14 restriction enzymes, which confirms the close relationships existing between these two species. T he nucleotidic sequence of the internal transcripted spacer (ITS1) bet ween rrs and rrl for the P. syringae pv. syringae strain CFBP1392 was determined. Restriction maps of the PCR-amplified ITS1 region were pre pared and compared for all 77 strains, Seventeen RFLP patterns, formin g three main clusters, were distinguished, One contained all strains o f P. syringae pv. tomato and of other pathovars which had been previou sly described as closely related by either pathogenicity studies or bi ochemical analyses. This cluster was equally far from P. viridiflava a nd from other P. syringae pathovars, These other pathovars of P. syrin gae formed a less coherent taxon.