First Report of Capsicum Chlorosis Virus Infecting Zinnia in the Continental United States

In September 2025, zinnia plants (Zinnia elegans and Z. hybrida) with chlorotic and necrotic ring spots characteristic of Orthotospovirus infection were observed in residential ornamental gardens in Payne County, Oklahoma, with about 50% incidence in a 5 m2 private garden. Additional symptomatic plants were collected in October from garden plantings in Cleveland County, with a weighted average incidence of 25% in a total of 10 m2, and in Oklahoma County, with 25% incidence in a 3 m2 public garden. Symptoms included concentric chlorotic and necrotic ringspots, sunken necrotic lesions, and irregular chlorotic patches on both leaf surfaces (Widana Gamage et al. 2016). Leaf samples from symptomatic plants (sample Zinnia-1, Zinnia-3, and Zinnia-1162) were collected, and total RNA was extracted using the RNeasy Plant Mini Kit (Qiagen). RT-PCR was performed using two primer sets, CaCV-F/R and CaCV-EP-F/R, which amplified the M RNA segment of Capsicum chlorosis virus (CaCV), species name: Orthotospovirus capsiciflavi. The CaCV-F (5′-ACTTTCCATCAACCTCTGT-3′) and CaCV-R (5′-GTTATGGCCATATTTCCCT-3′) primers were adopted from Sun et al. (2018) to yield an amplicon of approximately 828 bp. The CaCV-EP-F (5′-ATGYGATGTTGTKCCAATAAACAGAGC-3′) and CaCV-EP-R (5′-ACAYTTTGATGATAARAGTGCACATGA-3′) primers were designed using E-probe Diagnostic Nucleic acid Analysis (EDNA) (Espindola et al. 2021) to amplify a 1,149 bp region. Amplicons were purified using AMPure magnetic beads (BECKMAN) and Sanger-sequenced. No amplification was obtained from asymptomatic zinnia plants collected at the same locations or from non-template controls. BLASTn analysis showed that CaCV-EP-F/R amplicons from Zinnia-1 and Zinnia-3 (GenBank accessions PX620895-PX620896) shared 98% nucleotide identity with CaCV, segment M (MF469040.1), aligning to nt 818-1729 and nt 817-1729, respectively. Based on ORF annotation, both amplicons contained partial coding regions corresponding to the nonstructural movement protein (NSm gene) and the envelope glycoprotein (GnGc gene). In addition, CaCV-F/R amplicons from Zinnia-3 (PX620898) and Zinnia-1162 (PX620899) showed 99% nucleotide identity to CaCV isolate NRA, segment M (KX108864.1), aligning to nt 2990-3735 and nt 2996-3743, respectively (0 gaps). Both amplicons were mapped within the M-segment GP gene coding region, which produces the glycoprotein precursor. Based on these molecular results, the detected virus was identified as CaCV. This is the first confirmed report of CaCV infecting zinnia in Oklahoma and, to our knowledge, the first report of CaCV from the continental United States. CaCV has previously been reported infecting many important ornamental and crop species, including tomato and peanut in China (Chen et al. 2007; Huang et al. 2010), green pepper in Japan (Chiaki et al. 2020), and capsicum in Australia (Tsai et al. 2022). To our knowledge, this represents the first report of CaCV from the continental United States. The only U.S. report is CaCV infected Waxflower in Hawaii (Melzer et al. 2014). The detection of CaCV in ornamental zinnia plants in Oklahoma raises concerns about potential spillovers into solanaceous crops and suggests the need for further surveys in greenhouse and landscape settings to determine its distribution and vector associations in the region.