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Isolate Grand Haven (GH) 2 is a naturally occurring isolate of the chestnut blight fungus, Cryphonectria parasitica, that is greatly reduced in virulence due to the presence of a double-stranded RNA virus. Unlike many other virus-infected, hypovirulent isolates, GH2 is not substantially reduced in pigmentation, conidiation, or laccase expression compared to its virus-free counterpart. The dsRNA genome of the GH2 virus was cloned, sequenced, and compared to hypovirulence-associated viruses of the family Hypoviridae. GH2 dsRNA is considerably smaller than previously characterized members of the family, 9.8 kb compared to 12.5–12.7 kb for other members. The genome organization of GH2 dsRNA reflected the substantial difference in genome size. Like other members of the family, one strand contained a poly(A)⁺ tail at the 3′ end and a long sequence with several minicistrons at the 5′ end of the same strand …