Rice blast, caused by Magnaporthe oryzae is one of the most destructive rice diseases worldwide. The genetic variability of 55M. oryzae isolates from Iran and 32 isolates from Uruguay was analyzed using amplified fragment length polymorphism (AFLP). Cluster analysis using different grouping methods and similarity coefficients, based on the AFLP data from 679 monomorphic and polymorphic bands generated with eight primer combinations, was performed.The resulted grouping of the isolates revealed 4 separate AFLP lineages among a total of 87 isolate, designated as A1, A2, B, and C. Within each AFLP lineage, three or more clones were detected with a genetic similarity of 100 %. Overall genetic similarity was greater than 78 % between Iranian and Uruguayan populations. Evidence of gene flow between the Iranian and Uruguayan populations obtained from indica rice cultivars was observed as one Iranian isolate grouped lineage 1A together with Urugyayan isolates. Analysis of molecular variance (AMOVA) revealed that rice varietal type, sampling year and geographic region were the dominant factors determining genetic structure of M. oryzae populations; but rice cultivar had not significant effect.

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