Distribution map of rice blast fungus infected with mycoviruses. Mycoviruses with dsRNA genomes were found in 11 M. oryzae isolates from three provinces in the Mekong Delta region of Vietnam. The plant diagrams show the sites where disease lesions were sampled. The agarose gel shows viral dsRNA segments present in the infected M. oryzae isolates. Two mycoviruses were identified: MoCV1 had five dsRNA genomic segments of 2.6 kbp to 3.6 kbp, and a partitivirus had three segments of 1.8 kbp to 2.4 kbp. The M. oryzae isolates, S-0412-II 1a, S-0412-II 1c, and S-0412-II 2a, were infected with the MoCV1 strains, MOCV1-A, MOCV1-A-a, and MOCV1-B, respectively. Isolate S-0412-II 1c was also infected with the partitivirus.