First Report of <i>Solanum nigrum</i> as a Reservoir Host for <i>Potyvirus capsivenae</i> in mainland China

Potyvirus capsivenae (pepper veinal mottle virus, PVMV) is a potyvirus first described in Ghana in 1971 and subsequently reported in Africa and Asia. In China, it was first recorded in Taiwan in 2009. (Zhang et al. 2015) The natural hosts of PVMV are primarily solanaceous crops such as pepper, with occasional reports from cucurbit hosts. (Hu et al. 2020) Solanum nigrum is a widespread annual solanaceous weed in China. In June 2025, S. nigrum plants exhibiting chlorotic spots and leaf wrinkling were observed in a former pepper field in Xiangcheng Town, Gao’an County, Jiangxi Province. Three symptomatic leaf samples (SN75, SN78, and SN79) were pooled for ribosomal RNA-depleted RNA sequencing as described by Peng et al. (2019). A total of 32,556,811 clean reads was obtained and analyzed with VirusDetect, which identified only PVMV . Twenty-one contigs covered 92.9% of the PVMV reference genome (NC_011918) with 98.8% identity. The isolate from S. nigrum was designated PVMV-SN. De novo assembly with SPAdes yielded the complete genome sequence of PVMV-SN, which is 9,795 nt in length (GenBank accession PX680739). BLASTn analysis showed that the closest matches were PVMV isolates from Capsicum frutescens in Ghana (PV-0257, MZ405642; 98.6%), the reference isolate (NC_011918; 98.4%), and a tomato isolate from Taiwan (Tom1, PV476910; 98.3%). Based on the PVMV-SN genome sequence, a primer pair (P1 and P2) was designed to amplify the entire coat protein (CP) coding region (expected amplicon size: 1276 nt). RT-PCR was performed individually on the three original field samples included in the HTS pool; and all three tested positive. The CP nucleotide sequences obtained from the three field samples (SN75, SN78, and SN79) showed 99.1%, 99.4%, and 99.8% identity to one other, respectively. Compared with the CP nucleotide sequence derived from HTS (PX680739/SN-HTS), they shared 99.4%, 99.8%, and 100% identity, respectively. For pathogenicity assay, sap from SN79 was rub-inoculated onto Nicotiana benthamiana plants, which developed wrinkling and curling at 7 dpi and tested positive by RT-PCR. Sap from symptomatic N. benthamiana leaves was then rub-inoculated onto pepper (Capsicum annuum, cultivar Ganla 515), producing curling and chlorosis at 7 dpi and severe curling, chlorosis, wrinkling, and stunting by 14 dpi; RT-PCR and sequencing confirmed 100% identity with PX680739/SN-HTS. In 2025, 70 symptomatic pepper samples from five counties in Jiangxi Province were test, and 34 were positive for PVMV(48.6%). CP amplicons from three Gao’an isolates (GA2, GA3, and GA6) and two Nanchang isolates (CH5 and CH31) were sequenced. The Gao’an pepper isolates shared &gt;98.9% identity with three co-located S. nigrum samples and 99.8%–99.9% identity with isolate SN75, whereas the Nanchang isolates shared &gt;99.1% identity with these sequences. Phylogenetic analysis of CP gene sequences from the three S. nigrum and five pepper isolates from Jiangxi, together with 27 PVMV isolates retrieved from GenBank, showed that the three S. nigrum isolates and the three Gao’an pepper isolates formed a distinct clade, indicating a close phylogenetic relationship and suggesting that S. nigrum may serve as a potential reservoir for PVMV. To our knowledge, this is the first report of S. nigrum as a reservoir host for PVMV in mainland China. S. nigrum may therefore represent an important inoculum source in the epidemiology of PVMV in Chinese pepper production.