Viruses of the chestnut blight fungus, Cryphonectria parasitica

Viruses of Cryphonectria parasitica have been studied for more than 30 years because of their association with biologic control of the filamentous fungus that causes chestnut blight. One virus, Cryphonectria hypovirus 1 (CHV1), has been studied intensively and its manipulation has led to the discovery of considerable information about specific host-virus interactions. CHV1. was the prototype for description of the virus family Hypoviridae, the first virus family described whose members have no capsid. Three other virus species within this family as well as many strains of those species have since been identified. The different species vary in their genome organizations, in the degree to which they alter fungal virulence and phenotype, and in their natural occurrence. In addition to viruses in the family Hypoviridae, several other virus families have been identified in Cryphonectria. These have been less important from the standpoint of the natural history of the fungus and its biologic control but are important from a virological perspective. Among the most notable are viruses in the families Reoviridae, Narnaviridae, and Chrysoviridae. Hence, the filamentous fungus causing chestnut blight has become a rich source for the study of diverse viruses in a widespread and easily manipulable haploid organism.