ASSESSMENT OF GENETIC DIVERSITY OF THE CAUSAL AGENT OF BACTERIAL BROWN STRIPE OF RICE BY rep-PCR

Brown stripe of rice disease was first reported from rice nursery in Mazandaran province. The agent was identified as Acidovorax avenae subsp. avenae (Aaa) (Rahimian. 1986، Iran Agric. Res. 5:63-71). Assessment of the possible genetic diversity of Aaa isolates in eastern Mazandaran was attempted in the present study. On the basis of biochemical and physiological characteristics، the isolates were identified، phenotypically، as Aaa. All isolates were oxidase and catalase positive and hydrolysed starch، casein and Tween 80. They did not assimilate sucrose or salicin but were capable of using sorbitol and monnitol as carbon sources (Rahimian. 1986، Iran Agricultural Res. 5:63-71). Genomic DNA of isolates was extracted and subjected to rep-PCR using REP and BOX primers، under the previously described conditions with only minor modifications (Versalovic et al. 1991، Nucleic Acids Res. 19:6823-6831). Dendrograms were constructed using data sets obtained from amplified fragments، using the Jaccard coefficient، the UPGMA algorithm and NTSYS-PC program. Comparison of the genomic fingerprints demonstrated that، at 20%، 50%، 80% similarity levels isolates formed 7، 16، 23 clusters with BOX primer، respectively and 5، 13، 19 clusters with REP primer at the stated levels of similarity، respectively. The clusters produced in REP-PCR were highly congruent with those of BOX-PCR. There has been no report on the presence of such any high level of genetic diversity in this bacterial subspecies elsewhere