Evaluation of commercial genotypes of irrigated rice resistance to Magnaporthe oryzae

Presently, the knowledge of rice genotypes resistence to the main kinds of Magnaporthe oryzae causing rice blast, makes it a necessary to provide a base to control of blast disease by integrating a variety mixture composition as a new strategy among other means. The studying of physiologic kinds of fungus that affect rice genotypes on the field and on its pattern of virulence is important in developing resistance. In this way, 37 genotypes of irrigated rice were evaluated with the objective of testing the ten most prevailing races M. oryzae in Tocantins State. The plants were inoculated by the ten prevailing fungus species at 25 days after emerging. Spore multiplication was done on identified isolated spores using PDA culture. Virulence determination was done by using a visual note scale from 0 to 9. There were different plant genotype reactions to races inoculation. There was no races capable of infecting all studied rice genotypes for eight genotypes were resistant to all the races inoculation.