Structure and origin of Xanthomonas arboricola pv. pruni populations in western Europe
Xanthomonas arboricola pv. pruni (EPPO A2 list) was first described in North America in 1903. In Europe, it was first recorded in Italy in 1920. In France, the disease was observed in the 1990s in the southeast departments of Drôme and Gard (see EPPO RS 97/112). The disease was severe in 2000 and has continued to expand to new stone fruit orchards. Studies were done in France on the population genetics of X. arboricola pv. pruni to analyse its variability and better understand its origin. Strains from the USA, Italy, France (as well as a limited number of strains from Australia, Brazil, New Zealand and Uruguay) were studied using 3 complementary genomic tools (ITS region, 4 genes, FAFLP analysis). Results showed that population diversity was higher in the USA than in Italy and France. The same bacterial genotype was detected from 5 countries and 3 continents, a geographic distribution that can be explained by a human-aided migration of the pathogen. All data obtained supported the hypothesis that the pathogen originates from the USA and has subsequently been disseminated to Europe. In addition, it seemed more likely that X. arboricola pv. pruni was introduced to France via Italy.
Sources
Boudon S, Manceau C, Nottéghem JL (2006) Structure and origin of Xanthomonas arboricola pv. pruni causing bacterial spot of stone fruit trees in western Europe. Phytopathology 95(9), 1081-1088.