GENETIC DIVERSITY OF STRAINS OF Acidovorax oryzae CAUSAL AGENT OF BROWN STRIPE OF RICE IN MAZANDARAN PROVINCE

Brown  stripe  of  rice  is among the prevalent disease of rice seedling in Mazandaran and Guilan provinces.  For assessment  of  genotypical  diversity in  populations of the causative bacterium samples  were  collected  from rice seedbeds in the suburb of Sari, Mazandaran  province  in  2012. A total  of 90 isolates were recovered  and the phenotypic and genotypic characteristics of the causal bacterium were compared and identified as  Acidovorax  avenae  subsp.  avenae  ( Acidovorax oryzae). The isolates were fairly homogeneous in their physiological  and  biochemical features. They were differentiated into two and five groups , at similarity levels of 45% and 68%, respectively, in the whole cell protein electrophoretic profiles. Genomic DNA of isolates was obtained and subjected to rep-PCR ( with BOX and ERIC primers ) fingerprinting. Dendrograms were constructed, using the jacard coefficient, the UPGMA algorithm  and  NTSYS-PC  program.  Comparison  of  the  genomic  fingerprints demonstrated that, at 20%, 35% and 65% similarity levels isolates formed 2, 5 and 10 clusters with ERIC primer and at 20%, 50% and 80% similarity levels isolates formed 7, 16 and 23 clusters with BOX primer, respectively. The result indicates a high level of  genetic diversity in Ao populations.