Magnaporthe oryzae chrysovirus 1 strain D confers growth inhibition to the host fungus and exhibits multiform viral structural proteins

A Japanese isolate of Magnaporthe oryzae is infected by Magnaporthe oryzae chrysovirus 1-D (MoCV1-D), which is classified in cluster II of the family Chrysoviridae. The genome of MoCV1-D consists of five dsRNAs. dsRNAs 1–4 show high identity with those of related MoCV1 viruses, whereas dsRNA5 shows relatively low identity and is sometimes deleted during virus propagation. MoCV1-D causes growth inhibition of its host fungus, and the protein encoded by its dsRNA4 impairs cell growth when expressed in yeast cells. It also causes abnormal pigmentation and colony albinization, and we showed that these phenotypes are associated with reduced accumulation of the melanin biosynthesis intermediate scylatone. MoCV1-D exhibits multiform viral structural proteins during prolonged culture. The original host isolate is co-infected with MoCV1-D, a victorivirus, and a partitivirus, and these mycoviruses are detected in cell-free supernatant fractions after prolonged liquid culturing. Hyphal fusion experiments demonstrated that MoCV1-D is transmissible via anastomosis. •Rice blast in Japan was co-infected by chrysovirus, totivirus and partitiviruses.•Rice blast chrysovirus was transmissible to other individuals via anastomosis.•Nutrient starvation induced regular degradation of structural viral proteins.•Expression of mycoviral protein in S. cerevisiae induces cytological damage.•Viral genomic dsRNAs were released into extra-cellular phase after long-term culture.