First Report of Lychnis mottle virus Infecting Wild Tea ( Camellia taliensis ) in Yunnan, China

Lychnis mottle virus (LycMoV; genus Stralarivirus, family Secoviridae; RNA1, KR011032; RNA2, KR011033) is a bipartite positive-sense RNA virus previously reported from Lychnis spp. and associated with mottle symptoms (Fuchs et al. 2022; Yoo et al. 2015). Camellia taliensis (“Dali Cha”), a wild tea species, is known to harbor diverse viruses (Hao et al. 2018; Wang et al. 2023). In August 2018, nine leaf samples were collected from a single C. taliensis plant in Lincang City, Yunnan Province, China (23°44′15″N, 99°22′14″E). No foliar mottle, chlorosis, or growth abnormalities were observed. While no symptoms were observed, detection of putative viruses in economically important tea germplasm is significant for quarantine and breeding programs, as symptom expression may vary with environmental conditions or host genotype. Total RNA was extracted using the CTAB reagents (BBI Life Sciences, Shanghai, China) for each sample. After removal of ribosomal RNAs, cDNA libraries were prepared according to the standard protocol of Beijing Genomics Institute (Shenzhen, China) and subjected to rRNA-depleted high-throughput sequencing using BGISEQ-500 platform, generating 456.26 million paired-end 150 bp reads. Data processing was conducted as described by Xiao et al (2026) using merged sequencing reads generated from the nine samples. Briefly, raw reads were quality-filtered using fastp (version 1.0.1), assembled de novo using Trinity (version 2.15.1) with default parameters, and the assembled contigs were compared against the NCBI Virus RefSeq protein database (downloaded on August, 2025) using BLASTx (version 2.15.0) for virus identification. In addition to a previously reported Camellia taliensis betaflexivirus 1 (CtBV1), a 7,303-nt contig shared 87.88% identity with LycMoV, while a 3,803-nt contig showed 73.70% identity to Strawberry latent ringspot virus (SLRSV; RNA1, NC_006964; RNA2, NC_006965), suggesting a candidate isolate of LycMoV, tentatively named as Lychnis mottle virus Camellia isolate (LycMoV-Cam, provisionally designated as Tea virus S during the patent application process). The complete genome was obtained by 5′/3′ RACE and overlapping RT-PCR. The complete genome sequences were subsequently verified by Sanger sequencing. Excluding poly(A), RNA1 (GenBank OM365896) is 7,277 nt and encodes a 2,210-aa polyprotein containing conserved replication-associated motifs. RNA2 (GenBank OM365897) is 3,777 nt and encodes a 995-aa polyprotein. Maximum likelihood phylogenetic analysis using IQ-TREE3 with the best-fit model selected and 1000 bootstraps. The analysis was based on the conserved Pro–Pol region (between the “CG” motif of the 3C-proteinase and the “GDD” motif of RdRP) using representative members of Secoviridae and Picornaviridae. The resulting phylogeny placed LycMoV-Cam within the family Secoviridae. Pairwise comparisons revealed that the Pro–Pol region shared 94.47% amino acid identity with LycMoV and 91.15% with SLRSV, while the coat protein sequences shared 88.37% identity with LycMoV and 64.17% with SLRSV. According to the International Committee on Taxonomy of Viruses (ICTV) species demarcation criteria for Secoviridae (i.e., <75% identity in the combined coat protein or <80% identity in the Pro–Pol region), these results indicate that the presence of a novel isolate of LycMoV, designated LycMoV-Cam, infecting C. taliensis (Fuchs et al. 2022). LycMoV-Cam was detected in only one of nine leaf samples collected from a single C. taliensis plant (SRS11756855), suggesting that the virus may occur as a localized infection in the host plant. Of the 102,203,990 paired-end reads obtained, 240,117 and 374,131 read pairs mapped to RNA1 and RNA2, respectively, covering 99.92% of the genome, with mean depths of 6,564.79× and 19,633.43×. The higher depth for RNA2 may reflect differential accumulation of viral RNAs. CtBV1 was also detected in the same sample (65,637 reads; 99.82% coverage; 960.44× depth), suggesting a potential mixed infection. However, because the sampled C. taliensis plant was asymptomatic, the effect of co-infection on symptom development could not be determined in this study. RT-PCR using specific primers targeting the RNA1 segment (5′-GGAGTTGGGCTGAATAAGTG-3′/5′-AACCTTCACTGGTAGAGACGAC-3′) amplified a 727-bp fragment, confirming the presence of LycMoV-Cam. No obvious foliar symptoms were observed at the time of collection. However, LycMoV is associated with mottle symptoms in other hosts (Fuchs et al. 2022), and the potential impact on tea cultivation requires further investigation. Infectivity assays to assess transmission and symptom induction in C. taliensis and C. sinensis are planned. To our knowledge, this is the first report of LycMoV infecting Camellia taliensis in China, representing a significant expansion of the LycMoV host range from Caryophyllaceae to Theaceae and highlighting potential risks to commercial tea (C. sinensis) cultivation expanding the known host range of this virus.