First Report of Turnip mosaic virus Infecting Sesame ( <i>Sesamum indicum</i> ) in Korea

Sesame (Sesamum indicum) is an important oilseed crop widely cultivated in Asia and Africa (Zhang et al., 2012) and also meets substantial domestic demand in Korea. In July 2025, leaf tissues from three symptomatic sesame plants growing in a field in Andong, Gyeongsangbuk-do, South Korea, were collected. Symptoms included bright yellow mosaic, leaf puckering, distortion of young leaves, and downward curling. Most plants were symptomless and symptomatic plants occurred sporadically within the row. One lettuce (Lactuca sativa) plant growing adjacent to the sesame row showing severe leaf distortion, blistering, and curling was also collected. This study aimed to identify the virus(es) associated with these symptoms. Total RNA from three sesame and one lettuce plant 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. HTS data are available under accession PRJNA1366047. Reads were analyzed using CLC Genomics Workbench (Qiagen). Viral sequences corresponding to Lettuce big-vein virus (Varicosavirus lactucae), Plasmopara viticola lesion-associated ourmia-like virus 32, and a full-length genome of Turnip mosaic virus (TuMV; Potyvirus rapae) were recovered. Because the HTS library was prepared from pooled RNA, RT-PCR was performed on individual samples and confirmed that TuMV occurred exclusively in sesame, whereas the other two viruses were restricted to lettuce. TuMV belongs to the genus Potyvirus within the family Potyviridae and infects a broad range of cultivated and wild plant species (Nellist et al. 2022). The assembled TuMV genome shared 99.20% nucleotide identity with TuMV isolate CCLB (KR153038) and was deposited in GenBank under accession no. PX596814. For TuMV detection, newly designed primers targeting an approximately 400-bp region of the P3 protein (TuMV-F: ACACTATCGTGTTGGTGGC; TuMV-R: GAGCATGCCCATGAACCT) were used. The expected amplicon was obtained from all three sesame samples included in the pooled HTS library but not from lettuce. Eight additional symptomatic sesame plants collected from nearby fields were tested by RT-PCR, and five were positive. Amplicons from RT-PCR-positive samples were gel-purified and subjected to Sanger sequencing. The obtained sequences were identical and showed 100% nucleotide identity to the HTS-derived TuMV genome sequence (GenBank accession no. PX596814). A representative amplicon sequence was deposited in GenBank under accession no. PZ380310. These results confirm the presence of TuMV in symptomatic sesame plants. To our knowledge, this is the first report of natural infection of sesame by TuMV in Korea. As sesame is widely cultivated for edible seed and oil production, detection of TuMV under field conditions highlights the need for continued monitoring in sesame-growing regions.