Takuo Sawahata

Connecticut Agricultural Experiment Station, New Haven, Connecticut, United States

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Publications (2)6.91 Total impact

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    ABSTRACT: In general, mycoviruses are transmitted through hyphal anastomosis between vegetatively compatible strains of the same fungi, and their entire intracellular life cycle within host fungi limits transmission to separate species and even to incompatible strains belonging to the same species. Based on field observations of the white root rot fungus, Rosellinia necatrix, we found two interesting phenomena concerning mycovirus epidemiology. Specifically, apple trees in an orchard were inoculated with one or two R. necatrix strains that belonged to different mycelial compatibility groups (MCGs), strains W563 (virus-free, MCG139) and NW10 (carrying a mycovirus-like double-stranded (ds) RNA element (N10), MCG442). Forty-two sub-isolates of R. necatrix, which were retrieved 2-3 years later, were all genetically identical to W563 or NW10: however, 22 of the sub-isolates contained novel dsRNAs. Six novel dsRNAs (S1-S6) were isolated: S1 was a new victorivirus; S2, S3, and S4 were new partitiviruses; and S5 and S6 were novel viruses that could not be assigned to any known mycovirus family. N10 dsRNA was detected in three W563 sub-isolates. These findings indicated that novel mycoviruses, from an unknown source, were infecting strains W563 and NW10 of R. necatrix in the soil, and that N10 dsRNA was being transmitted between incompatible strains, NW10 to W563.
    FEMS Microbiology Ecology 07/2012; · 3.56 Impact Factor
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    ABSTRACT: A colony-print immunoassay (CPIA) using an anti-dsRNA antibody was developed to visualize the distribution of four unrelated mycoviruses with dsRNA genomes, a partitivirus (RnPV1), mycoreovirus (RnMyRV3), megabirnavirus (RnMBV1), and an unidentified virus (RnQV1), in mycelia of the white root rot fungus, Rosellinia necatrix. CPIA revealed different distribution patterns within single colonies for each virus. Both RnPV1 and RnMBV1 were distributed throughout single colonies, RnMyRV3 was absent from some colony sectors, and RnQV1 exhibited varied accumulation levels between sectors. RnMyRV3 and RnQV1 were transmitted to the recipient virus-free colonies of virus-infected and virus-free colony pairs more slowly than were RnPV1 or RnMBV1. The presence of RnMyRV3 in recipient colonies restricted horizontal transmission of RnPV1 and RnMBV1. These results imply that one or more mechanisms are present in host-virus and virus-virus interactions that restrict the spread of viruses within and between colonies.
    Virology 11/2010; 409(2):280-9. · 3.35 Impact Factor