Identification of non-pathogenic Xanthomonas strains associated with plants

A total of 70 presumptive non-pathogenic yellow-pigmented strains from different origins were identified to the genus Xanthomonas with the genus-specific monoclonal antibodies (XI and XII), and fatty acid methyl ester (FAME) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) protein databases. On the basis of FAME profiles and SDS-PAGE protein patterns, these non-pathogenic xanthomonads formed a heterogeneous population. Fourty-two strains were identified as the same species by both methods, whereas five strains were identified as different species. Only eight strains remained unidentified by both methods, whereas in 15 cases the identification was ambiguous. The identification at pathovar level was usually ambiguous and nor concordant, which indicated that the non-pathogenic xanthomonads cannot be classified in the described pathovars. None of the non-pathogenic xanthomonads was identified as belonging to the pathovars of the plant from which they were isolated.