First record of a negative single stranded RNA viruses from entomopathogenic fungus Beauveria bassiana Vuillemin

Abstract Beauveria bassiana Vuillemin is an entomopathogenic fungus that has been developed as a biological insecticide and used worldwide. B. bassiana can be infected by one or more mycoviruses, which are generally double stranded RNA viruses (dsRNA), but single stranded RNA virus (ssRNA) infection has been rarely reported, especially negative single stranded RNA viruses (-ssRNA). In the present study, we sequenced and analyzed the whole genomes of two different nucleic acid types of mycoviruses that co-infected one B. bassiana strain, which are -ssRNA and dsRNA, namely Beauveria bassiana negative transcribed RNA virus 1 (BbNSRVs1) and Beauveria bassiana dsRNA mycovirus 1 (BbdsRNAMV1), respectively. The genome of BbNSRVs1 consists of a -ssRNA segment with a length of 6169 bp harboring a single open reading frame (ORF), which encodes a putative RNA dependent RNA polymerase (RdRp) with 1949 aa (220.1 kDa), it showed the highest homology of 59.79% to that of PvLamonoambiV2 belongs to family Monoegalales according to a BLASTx analysis. This is the first report of -ssRNA mycovirus in B. bassiana. The genome of BbdsRNAMV1 consists of two dsRNA fragments with 2164 bp and 1765 bp in length, respectively, the dsRNA1 of which encodes a conserved RdRp motif, with a BLASTx homology of 70.75% to that of a taxonomically undetermined mycovirus Fusarium graminearum dsRNA mycovirus 5 (FgdsRNAMV5), and the dsRNA2 encodes a coat protein (CP) motif, with a BLASTx homology of 64.26% to that of the FgdsRNAMV5. Therefore, the status of virus BbdsRNAMV1 was taxonomically undetermined.