<i>Bidens</i> <i>pilosa</i> Is a New Natural Host of Telosma Mosaic Virus in China

Telosma mosaic virus (TelMV), a member of the genus Potyvirus (family Potyviridae), is an emerging virus infecting a variety of natural hosts. This virus has been reported to infect Passiflora edulis (Chiemsombat et al. 2014), Pogostemon cablin (Noveriza et al. 2016), Senna alata L. (Yao et al. 2018), and Telosma cordata (Ha et al. 2008), with passion fruit (Passiflora edulis) being its primary host in parts of Asia. In October 2023, a field survey was conducted in passion fruit orchards in Beihai, Guangxi province, China, virus-like symptoms such as chlorosis and mottling of leaves were observed in both passion fruit and adjacent Bidens pilosa L. plants. The virus-like Bidens pilosa L. sample (named as BH-GZC) was collected from a location where the TelMV-infected passion fruit had previously been confirmed. In order to confirm the causal viral pathogen in BH-GZC, total RNA was extracted and subjected to reverse transcription polymerase chain reaction (RT-PCR) with TelMV-specific primers (TelMV-F1: 5’-AGAAGAGTTGTGGTTTATGTCACA-3’; TelMV-R1: 5’-TGGGACAACAAACATTAAGGCA-3’). A target amplicon with the length of 1456-bp was obtained. The amplicon was then cloned into pEASY-Blunt Zero Cloning Vector (Transgen, Beijing) and sequenced (GenBank accession no. PV948061). Sequence alignment revealed that the BH-GZC sequence shared 99% nucleotide identity to three TelMV isolates (GenBank accession nos. ON932196.1, OR786366.2, and KJ789129.1). BH-GZC was therefore identified as an isolate of TelMV and named as TelMV-GZC. Additionally, to assess the infectivity of TelMV-GZC, sap from homogenized infected leaves in phosphate buffer (0.1 M, pH 7.0) was mechanically inoculated onto 10 healthy Bidens pilosa L. seedlings. Within 10 days post-inoculation, two plants developed symptoms consistent with field observations, while buffer-inoculated controls remained asymptomatic. RT-PCR confirmed TelMV presence in symptomatic plants, fulfilling Koch’s postulates. To our knowledge, this is the first report identifying Bidens pilosa L. as a new natural host for TelMV. Bidens pilosa L. may function as intermediate hosts for viruses that could infect crops and provide habitats for insect vectors within plantations. These findings highlight the urgent need for timely removal of Bidens pilosa L. from plantations to disrupt viral transmission pathways and mitigate disease spread.