The presence of viruses is less explored in Mucoromycota as compared to other fungal
groups such as Ascomycota and Basidiomycota. Recently, more and more mycoviruses are
identified from the early-diverging lineages of fungi. We have determined the genome
of 11 novel dsRNA viruses in seven different Umbelopsis strains with next-generation
sequencing (NGS). The identified viruses were named Umbelopsis ramanniana virus 5
(UrV5), 6a (UrV6a); 6b (UrV6b); 7 (UrV7); 8a (UrV8a); 8b (UrV8b); Umbelopsis gibberispora
virus 1 (UgV1); 2 (UgV2) and Umbelopsis dimorpha virus 1a (UdV1a), 1b (UdV1b) and
2 (UdV2). All the newly identified viruses contain two open reading frames (ORFs),
which putatively encode the coat protein (CP) and the RNA-dependent RNA polymerase
(RdRp), respectively. Based on the phylogeny inferred from the RdRp sequences, eight
viruses (UrV7, UrV8a, UrV8b, UgV1, UgV2, UdV1a, UdV1b and UdV2) belong to the genus
Totivirus, while UrV5, UrV6a and UrV6b are placed into a yet unclassified but well-defined
Totiviridae-related group. In UrV5, UgV1, UgV2, UrV8b, UdV1a, UdV2 and UdV1b, ORF2
is predicted to be translated as a fusion protein via a rare +1 (or-2) ribosomal frameshift,
which is not characteristic to most members of the Totivirus genus. Virus particles
31 to 32 nm in diameter could be detected in the examined fungal strains by transmission
electron microscopy. Through the identification and characterization of new viruses
of Mucoromycota fungi, we can gain insight into the diversity of mycoviruses, as well
as into their phylogeny and genome organization.