Coinfection of Gynura bicolor with a New Strain of Vanilla Distortion Mosaic Virus and a Novel Maculavirus in China

In recent years, symptoms suggestive of viral infection have commonly occurred in <i>Gynura bicolor</i> in China. However, no viral genome infecting <i>G. bicolor</i> has been reported. This study applied high-throughput sequencing to plant samples with chlorotic spots in Sanya, Hainan. Viral sequences were confirmed using RT-PCR and RACE. Complete genomes of vanilla distortion mosaic virus (VDMV, <i>Potyvirus vanillae</i>) and an unknown virus were obtained. Sequence analysis indicated that the VDMV isolate from the <i>G. bicolor</i> is a novel variant. It shares 81.13% identity with its closest known strain. The unknown virus is phylogenetically related to maculaviruses but shares less than 76% nucleotide identity with other tymovirids. According to the ICTV, it should be classified as a new member of the genus <i>Maculavirus</i>. In this study, we provisionally designated the virus as gynura bicolor maculavirus (GBMV). Transmission electron microscopy revealed both filamentous and icosahedral virions in stems, but only filamentous virions in leaves. Quantitative RT-PCR showed high RNA accumulation of both viruses in the stems. GBMV levels were significantly lower in leaves. Dodder-mediated mechanical transmission successfully transferred VDMV and GBMV to <i>Nicotiana occidentalis</i>, <i>Oenothera biennis</i>, and <i>Chenopodium amaranticolor</i>. <i>O. biennis</i> developed chlorotic symptoms 15 days after dual infection.