A second quadrivirus strain from the phytopathogenic filamentous fungus Rosellinia necatrix

We report the biological and molecular characterisation ofa second quadrivirus strain termed Rosellinia necatrix quadrivirus 1 strain W1118 (RnQV1-W1118) from the ascomycete white root rot fungus. Commonalities with the first quadrivirus (RnQV1-W1075) include its quadripartite genome structure, spherical particle morphology, sequence heterogeneity in the extreme terminal end, 72–82%sequence identity between the corresponding proteins, and its ability to cause a latent infection. Distinguishing features include different conserved terminal sequences and the degree of susceptibility of two major capsid proteins to proteolytic degradation, which is thought to occur during virion purification. Identification of this second quadrivirus strain strengthens our earlier proposal that ‘‘Rosellinia necatrix quadrivirus 1’’ should be considered the type species of a novel family, ‘‘Quadriviridae’’.