Genomic Variability of the Xanthomonas Pathovar mangiferaeindicae, 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 Reunion, indicating that pepper tree may not be an alternate host for Xanthomonas pv. mangiferaeindicae strains.