DNA-FINGERPRINTING OF INDIAN ISOLATES OF XANTHOMONAS-ORYZAE PV ORYZAE

A high level of genetic polymorphism was detected among Indian isolate s of Xanthomonas oryzae pv. oryzae using hypervariable probes such as a microsatellite oligonucleotide, probe (TG)(10), a human minisatellit e probe, pV47, an avirulence gene probe, avrXa10 and a repeat clone, p BS101. These DNA probes detected multiple loci in the bacterial genome generating complex DNA fingerprints and differentiated all of the bac terial isolates. Analysis of fingerprints indicated that pV47, (TG)(10 ) and pBS101 have a lower probability of identical match than avrXa10 and therefore are potential probes for DNA fingerprinting and variabil ity analysis of Xanthamonas oryzae pv. oryzae pathogen populations. Cl uster analysis based on hybridization patterns using all of the above probes showed five groups at 56% similarity. Studies on the methylatio n patterns of isolates representing the three important races of X. or yzae pv. oryzae indicated more methylation in the most virulent isolat e, suggesting a possible role of methylation in pathogenicity.