PFGE: a tool for examination of heterogeneity between the bacterial spot-causing xanthomonads of tomato plants in Bulgaria.

Pulsed-field gel electrophoresis (PFGE) is a highly discriminative molecular typing method that is used for epidemiological studies and investigation of outbreaks caused by different pathogens, including phytopathogenic Xanthomonas species. Bacterial spot (BS) is the most common and one of the most destructive diseases of tomato and pepper plants in Bulgaria. Several Xanthomonas species are known to cause BS, but the global distribution and genetic diversity of these species are not well understood. A collection of 100 BS-causing strains, isolated during the period of 1985-2012 from different tomato cultivars and weeds associated with tomato production areas from 11 geographic regions in Bulgaria, were screened for genetic diversity by genomic DNA restriction with rare-cutting endonucleases (XbaI and SpeI) subsequently resolved by PFGE. Two haplotypes for Xanthomonas vesicatoria and one haplotype for Xanthomonas gardneri strains were found.