The knowledge of the occurrence and distribution of races of Pyricularia grisea is important in rice (Oryza sativa) breeding programs. However, for the correct identification of the races of the pathogen and to compare them with other reports, it is necessary to utilize race differential genotypes that exhibit identical genetic characteristic and source. The main objective of this work was compare the genetic variation of two genotypes of Raminad Str. 3 utilized as one of the eight international differentials and to examine the race composition of P. grisea in the State of Rio Grande do Sul, Brazil. Of 39 microsatellite markers used to verify the genetic differences between the two genotypes identified as the Raminad Str. 3, 20 exhibited polymorphism. The race determination was based on the reaction of differentials submitted to inoculation with 85 monosporic isolates from 14 rice growing municipalities of Rio Grande do Sul. The infection types were scored according to the standard evaluation international system for rice diseases, 14 days after inoculation.
