Development of Lateral Flow Reverse Transcription Recombinase Polymerase Amplification (LF-RT-RPA) Assay for On-site Detection of Cucumber Mosaic Virus on Cnidium officinale

Background: Quality and quantity of Cheongung (Cnidium officinale Makinoi) is reduced by plant viral infections. Therefore, it is necessary to develop effective detection methods for diagnosis of problematic viruses in Cheongung farms. This study aimed to develop lateral flow reverse transcription recombinase polymerase amplification (LF-RT-RPA) assay for the detection of cucumber mosaic virus (CMV) in C. officinale. Methods and Results: Total RNA was extracted from CMV-infected Cheongung plant and sub-jected to RT-RPA reaction with RPA_CMV-CP-F1/R1 primers targeting the CMV RNA3 sequence. When specificity was examined using lateral flow Immunostrip, experimental and control lines were generated only in the sample from the CMV-infected plant, while control lines were observed in samples from cnidium vein yellowing virus-1, cnidium vein yellowing virus-2, and apple stem grooving virus-infected Cheongung plants. The optimal temperature and reaction time for LF-RT-RPA assay were determined to be 37^oC and 15 min. On-site diagnosis carried out to detect CMV in 7 Cheongung plants showing viral-infection symptoms, confirmed six of the plants infected with CMV. Conclusion: CMV, one of the prevalent plant viruses, was effectively detected using LF-RT-RPA assay without the need of any equipment on farms. Detection limit for CMV in C. officinale Maki-noi was up to 100 fg of total RNA, suggesting that the LF-RT-RPA assay developed in this study is suitable for on-site detection of CMV in Cheongung farms.