Development of a PCR Diagnostic System for Iris yellow spot tospovirus in Quarantine

Development of a sensitive Luminex xMAP-based microsphere immunoassay for specific detection of Iris yellow spot virus

BACKGROUND

Iris yellow spot virus (IYSV) is an Orthotospovirus that infects most Allium species. Very few approaches for specific detection of IYSV from infected plants are available to date. We report the development of a high-sensitive Luminex xMAP-based microsphere immunoassay (MIA) for specific detection of IYSV.

RESULTS

The nucleocapsid (N) gene of IYSV was cloned and expressed in Escherichia coli to produce the His-tagged recombinant N protein. A panel of monoclonal antibodies (MAbs) against IYSV was generated by immunizing the mice with recombinant N protein. Five specific MAbs (16D9, 11C6, 7F4, 12C10, and 14H12) were identified and used for developing the Luminex xMAP-based MIA systems along with a polyclonal antibody against IYSV. Comparative analyses of their sensitivity and specificity in detecting IYSV from infected tobacco leaves identified 7F4 as the best-performed MAb in MIA. We then optimized the working conditions of Luminex xMAP-based MIA in specific detection of IYSV from infected tobacco leaves by using appropriate blocking buffer and proper concentration of biotin-labeled antibodies as well as the suitable ratio between the antibodies and the streptavidin R-phycoerythrin (SA-RPE). Under the optimized conditions the Luminex xMAP-based MIA was able to specifically detect IYSV with much higher sensitivity than conventional enzyme-linked immunosorbent assay (ELISA). Importantly, the Luminex xMAP-based MIA is time-saving and the whole procedure could be completed within 2.5 h.

CONCLUSIONS

We generated five specific MAbs against IYSV and developed the Luminex xMAP-based MIA method for specific detection of IYSV in plants. This assay provides a sensitive, high-specific, easy to perform and likely cost-effective approach for IYSV detection from infected plants, implicating potential broad usefulness of MIA in plant virus diagnosis.

Development of a Specific Diagnostic System for Detecting Turnip Yellow Mosaic Virus from Chinese Cabbage in Korea

Turnip yellow mosaic virus (TYMV) is a plant pathogenic virus transmitted mainly through its host Brassica spp. TYMV is originated from Europe. Its infection cases have been reported in Australia, Brazil, Turkey, and Japan. Symptoms similar to those of TYMV infections were also reported in Korea in 2012. In this study, we developed RT-PCR primer pairs that were highly sensitive for detecting TYMV. The developed RT-PCR primer pairs offered about 10-100 times stronger detection sensitivity compared to primer pairs previously used in Korea. As a result, a 491 bp TYMV-specific band was identified. The specific band was confirmed to be TYMV based on sequencing results and phylogenetic analysis. The RT-PCR primer pairs developed in this study can be used to rapidly and precisely diagnose TYMV in agricultural products such as Chinese cabbage and other crops infected by TYMV.

Development of Nested PCR-Based Specific Markers for Detection of Peach Rosette Mosaic Virus in Plant Quarantine

The Peach rosette mosaic virus (PRMV) is a plant pathogen of the genus Nepovirus, and has been designated as a controlled quarantine virus in Korea. In this study, a specific reverse transcription (RT)-PCR marker set, nested PCR marker set, and modified-plasmid positive control were developed to promptly and accurately diagnose PRMV at plant-quarantine sites. The final selected PRMV-specific RT-PCR marker was PRMV-N10/C70 (967 bp), and the nested PCR product of 419 bp was finally amplified. The modified-plasmid positive control, in which the SalI restriction-enzyme region (GTCGAC) was inserted, verified PRMV contamination in a comparison with the control, enabling a more accurate diagnosis. It is expected that the developed method will continuously contribute to the plant-quarantine process in Korea.

Loop-mediated Isothermal Amplification Assay to Rapidly Detect Wheat Streak Mosaic Virus in Quarantined Plants

We developed a loop-mediated isothermal amplification (LAMP) method to rapidly diagnose Wheat streak mosaic virus (WSMV) during quarantine inspections of imported wheat, corn, oats, and millet. The LAMP method was developed as a plant quarantine inspection method for the first time, and its simplicity, quickness, specificity and sensitivity were verified compared to current reverse transcription-polymerase chain reaction (RT-PCR) and nested PCR quarantine methods. We were able to quickly screen for WSMV at quarantine sites with many test samples; thus, this method is expected to contribute to plant quarantine inspections.

Development of PCR diagnostic system for detection of the seed-transmitted tobacco ringspot virus in quarantine

Tobacco ringspot virus (TRSV) is a plant quarantine virus in Korea. As such, a TRSV examination is conducted when importing various crops. In this study, RT-PCR and nested PCR systems for TRSV detection in quarantine sites, and the modified-positive control plasmid for proving laboratory contamination and false positive reactions were developed. The developed diagnostic system was used to detect TRSV in the quarantine site. It revealed that from 2012 to August 2014, a total of 12 cases were detected in imported various crops. The system is expected to continue contributing to TRSV detection in plant quarantine.