First Report of Tobacco etch virus Infecting Dragon Fruit ( <i>Hylocereus undatus</i> ) in China

Dragon fruit (Hylocereus undatus), a perennial woody Cactaceae species, is an economically important horticultural crop (Wang et al. 2022). Reported dragon fruit-infecting viruses include cactus virus X, zygocactus virus X, and Pitaya virus X (Espinoza-Lozano et al. 2024). Tobacco etch virus (TEV; species Potyvirus nicotianainsculpentis family Potyviridae) is nonpersistently aphid-transmitted, with a broad host range of 149 species across 19 families (primarily Solanaceae). TEV was first reported in pepper (Capsicum annuum) in China (1986), coleus (Coleus blumei) in the U.S. (Lockhart et al. 2010), and Senna multiglandulosa in Mexico (Ortega-Acosta et al. 2023). TEV susceptibility is confirmed in some Cactaceae, but its dragon fruit infection potential remains uninvestigated despite ongoing host range expansion.In July 2023, dragon fruit plants with irregular chlorotic spots and etch-like cladode lesions were observed in a ≈0.5 ha commercial plantation in Yuanjiang County, Yuxi, Yunnan (30% disease incidence). Symptomatic cladode tissues from five individual plants were collected for pathogen identification. Total RNA was extracted with a plant RNA kit (Omega Bio-tek, Norcross, GA, U.S.A.). For high-throughput sequencing (HTS) library construction, equal RNA amounts from each of the five individual samples were pooled, with sequencing performed on an Illumina HiSeq 2500 platform. Trimmomatic-trimmed clean reads (11,673,514) were de novo assembled into 53,407 contigs via Trinity. BLASTn analysis of 251 virus-like contigs identified a 9,531-nt contig with 94.19% identity to the TEV reference genome (M15239.1). Clean read mapping to the assembled TEV genome yielded 187× mean depth and 100% genome coverage. Virome analysis detected no other known plant viruses, including reported dragon fruit-infecting viruses, confirming single TEV infection in the samples.RT-PCR validation was performed with TEV coat protein (CP)-targeting specific primers. The expected 738 bp amplicon was amplified from all 5 recollected symptomatic samples, with PCR products cloned into the pGEM-T vector (Promega Corporation, Fitchburg, WI, U.S.A.). Viral genome 5′ and 3′ ends were amplified via a 5′/3′ RACE Kit (Sangon Biotech, Shanghai, China). All amplified fragments were Sanger-sequenced (Sangon Biotech) to obtain the complete TEV genome. The 9,531 nt full-length genome shared 99.75% identity with the de novo assembled contig. This isolate (TEV-YNs; GenBank:PX934430) had 93.91% nucleotide and 86.10% polyprotein amino acid identity to TEV isolate 7DA (DQ986288), exceeding Potyvirus species demarcation thresholds (&lt;76% nt, &lt;82% aa identity), confirming it as a severe TEV etch strain. Enzyme-linked immunosorbent assay (ELISA) with a commercial TEV kit (Agdia, Elkhart, IN, U.S.A.), using healthy dragon fruit as negative control and TEV-infected tobacco as positive control, showed all five symptomatic samples were positive, consistent with RT-PCR results.To our knowledge, this is the first global and Chinese report of natural TEV infection in dragon fruit. This finding expands TEV’s host range to an economically important Cactaceae species, highlights TEV transmission risk between solanaceous crops (e.g., tobacco) and dragon fruit in Yunnan co-cultivation regions, and provides a critical foundation for dragon fruit TEV detection and management strategies.