First Report of Cucumber mosaic virus Infecting <i>Helianthus annuus</i> in Korea

Sunflower (Helianthus annuus L.) is one of the most important globally cultivated oilseed crops that is valued for its nutritional, medicinal, and commercial uses (Adeleke and Babalola 2020). In July and August 2025, sunflower plants showing mosaic, mottling, chlorosis, and mild distortion were observed in a home garden in Andong, Gyeongsangbuk-do, Korea, where 4 of 5 plants (80%) were symptomatic. Two symptomatic plants were sampled for further analysis. Total RNA from both samples was extracted using the iQeasy RNA Extraction Kit (iNtRON, Korea). RNA concentrations were normalized, pooled, and submitted to Macrogen (Seoul, Korea) for library preparation and high-throughput sequencing (HTS) on an Illumina platform. SRA data is available under accession PRJNA1367370. The resulting reads were analyzed using CLC Genomics Workbench (Qiagen). Cucumber mosaic virus (CMV; Cucumovirus CMV) is the only virus identified and its full genome has been submitted to GenBank under accession numbers PX596811-PX596813. CMV is a tripartite virus that belongs to the genus Cucumovirus in the family Bromoviridae. It was first identified in 1916 and is now known to infect more than 1,300 plant species including many major crops worldwide (Scholthof et al. 2011). The assembled CMV RNAs (RNA1, RNA2, and RNA3) shared 99.46%, 99.84%, and 99.64% nucleotide identity with reference sequences KC527807, KC527708, and KC527748, respectively. The presence of CMV was verified by RT-PCR targeting the coat protein region. A newly designed primer pair, CMV-F (5′-CGCAGGTGGTTAACGGT-3′) and CMV-R (5′-CCACACGGTAGAATCAAAT-3′), yielding a 697-bp product, produced clear amplicons of the expected size. The clearest band was gel purified, followed by Sanger sequencing by Macrogen. The obtained sequences showed 98.98% nucleotide identity to CMV isolate OD291J (LC066437). To assess the extent of infection, eight additional sunflower samples, both symptomatic and asymptomatic, were collected from three new locations in Andong. RT-PCR confirmed the presence of CMV in six of the eight samples. To our knowledge, no molecularly verified infection of cultivated sunflower by CMV has been previously reported. A historical USDA account from Beltsville, Maryland, listed CMV as a pathogen of the wild perennial sunflower species, H. decapetalus var. multiflorus. However, these early observations, which predate modern serological and molecular methods, do not confirm CMV infection in cultivated sunflowers. Furthermore, no CMV sequences originating from sunflowers were found in the NCBI Virus database. In light of these findings, we report the first confirmed detection of CMV infecting cultivated sunflowers. Sunflower is an increasingly important global crop, producing over 56 million metric tons annually and thriving across diverse environments. The identification of CMV in sunflowers raises an important alert, as CMV is a widespread pathogen with the potential to affect crop health and productivity.