Fingerprinting genome of Xanthomonas campestris pv. glycines strains by using random amplified Polymorphic DNA (RAPD) assay

One hundred and twenty-seven strains of Xanthomonas campestris pv. glycines, the causal agent of soybean bacterial pustule, isolated from different regions in the country were analysed for their genome, plasmid and virulence diversities. Random amplified polymorphic DNA (RAPD) analyses of the genomic DNA using polymerase chain reaction (PCR) with 6 selected from 40 primers indicated that these strains were identified into 10 distinct RAPD type fingerprint (RAPD reaction type A to J). Identical fingerprints were detected among 65.07 percent of 127 strains tested. Strains of RAPD reaction type A were rare and found primarily in North East of soybean growing region, accounting for only 2.3 percent RAPD type B was most common with 40.94 percent. No relationship among RAPA reaction type and soybean growing region was observed. We conclude that these strains are genetically and heterogeneous. When they were investigated on plasmid, only 96 strains harboured megaplasmid (s) and could be divided into 4-distinct size classes (K to N) as determine by electrophoretic mobility in agarose gels. The number of plasmid per strains varied from one to six. A total of one hundred and sixty-eight plasmid bands with size over marker and 12,216 to 1,638 Kb were identified. Strains that had identical plasmid profiles analyses however, was no good agreement with RAPD reaction type. Xanthomonas campestris pv. glycines strains were also screened for their ability to cause pustule lesion on SJ4 variety of soybean under greenhouse conditions. Variability in severity of disease reaction among 127 strains were determined into 3 levels of weakly, moderately and strongly aggressive strains. There was highly related between disease reaction and results of RAPD reaction type but less relation between disease reaction and plasmid profile was performed. Both assays of symptom expression and RAPD were capable of distinguishing strongly-from weakly aggressive strains where the correlation between the presence of plasmid (s) and the variability of pathogenicity remain to be determined.