The complete genomic sequence of a novel megabirnavirus from Fusarium pseudograminearum, the causal agent of wheat crown rot

A novel double-stranded RNA (dsRNA) mycovirus, named Fusarium pseudograminearum megabirnavirus 1 (FpgMBV1), was found in a hypovirulent strain FC136-2A of Fusarium pseudograminearum, the causal agent of wheat crown rot. The complete genome of FpgMBV1 comprised two dsRNA segments, L1-dsRNA (8951 bp) and L2-dsRNA (5337 bp). Both dsRNAs carry two open reading frames on the positive strand. L1-dsRNA potentially encodes a 131.3-kDa coat protein (CP) and a 126.3-kDa RNA-dependent RNA polymerase (RdRp), while L2-dsRNA encodes two putative proteins of 97.2 kDa and 30.6 kDa with unknown functions. As found in members of the family Megabirnaviridae, the 5’- and 3’-terminal sequences of L1-dsRNA and L2-dsRNA of FpgMBV1 are highly conserved. The identity between L1-dsRNA (1630 nt) and L2-dsRNA (1682 nt) is 88.95%, and the first 236 nt (nt 1-236) are exactly identical. The 3’ UTRs of L1-dsRNA (155 nt) and L2-dsRNA (109 nt) are 66.67% identical, with identical terminal hexamer sequences (5’-AAAAGC-3’). Phylogenetic analyses based on the amino acid sequences of the RdRps indicated that FpgMBV1 is a new member of the family Megabirnaviridae.