Identification of a putative novel carlavirus infecting Gynura bicolor in China

In July 2023, 25 leaf samples of Gynura bicolor showing mosaic and chlorosis symptoms were collected in Hohhot, Inner Mongolia, China. Total RNA was extracted from pooled, homogenized tissues was subjected to high-throughput sequencing (HTS), which revealed the presence of four known viruses and an unknown virus. The complete genome sequence of the unknown virus was obtained using RT-PCR and RACE, yielding an 8,750-nt positive-sense single-stranded RNA genome with six open reading frames. Sequence analysis revealed that its replicase gene shared 71.6% nucleotide and 78.4% amino acid sequence identity with pseudostellaria heterophylla carlavirus 1 (PhCV1). These values are below the species demarcation threshold. Phylogenetic analysis grouped the virus with members of the genus Carlavirus, supporting its classification as a novel member of this genus. We have tentatively designeatd it "gynura bicolor carlavirus" (GbCV). This is the first report of a carlavirus infecting G. bicolor.