Complete genome sequence of a previously undescribed badnavirus occurring in Polyscias fruticosa L. (Ming aralia)

A previously undescribed badnavirus was identified in plants of Polyscias fruticosa (Ming aralia) showing symptoms of mild mosaic and leaf senescence. Characteristic bacilliform virions of the Polyscias badnavirus averaging 30 × 120 nm in size were observed by transmission electron microscopy in partially purified leaf tissue extracts from symptomatic but not asymptomatic plants collected in the USA and Nigeria. The isolate from the USA was complete sequenced. The genome is 7592 bp in length and contains three open reading frames with an arrangement similar to that of other members of the genus Badnavirus. The largest open reading frame (ORF3) encodes a putative polyprotein, with predicted domains including zinc finger, aspartic protease, reverse transcriptase (RT) and RNase H, in that order. The USA and Nigeria isolates of the virus had a high level (98%) of nucleotide sequence identity in the RT+RNase H region. Within the genus Badnavirus, these viruses were most closely related to schefflera ringspot virus (SRV), sharing 63% identity at the nucleotide level. Based on the ICTV species demarcation criteria for the genus Badnavirus (more than 20% nucleotide sequence divergence in the RT+RNase H region), the Polyscias virus is proposed to be a new member of the genus, and the name polyscias mosaic virus (PoMV) is proposed. The complete genome sequence was deposited in the NCBI GenBank database under accession no. MH475918.