Genomic variability of the Xanthomonas pathovar mangiferaeindica, agent of mango bacterial black spot

The genetic diversity of 138 strains of the #Xanthomonas# pathovar mangiferaeindicae, which were isolated from three different hosts (mango, ambarella, and pepper tree) in 14 different countries, was assessed with restriction fragment length polymorphism markers. An analysis of patterns obtained by hybridization with an #hrp# cluster probe from #Xanthomonas oryzae# pv. oryzae separated 11 of the strains from all of the other strains, which suggested that these 11 strains may not be #Xanthomonas# pv. mangiferaeindicae strains. Hybridization with an avirulence gene from #X. oryzae# pv. oryzae and a repetitive DNA fragment from #Xanthomonas# pv. mangiferaeindicae separated the remaining 127 strains into four groups that were consistent with both geographic and host origins. The group with the greatest diversity consisted of strains from Southeast Asia, where mango originated. Other groups and subgroups contained strains that were either from widely separated countries, which suggested that wide dissemination from a single site occurred, or from localized areas, which suggested that evolution of separate lineages of strains occurred. One group of strains contained only strains isolated from pepper trees in Réunion, indicating that pepper tree may not be an alternate host for #Xanthomonas# pv. magiferaeindicae strains. (Résumé d'auteur