Serological and Molecular Assays for Rapid and Sensitive Detection of Iris yellow spot virus Infection of Bulb and Seed Onion Crops.

Iris yellow spot virus (IYSV) has spread rapidly in the United States and has become an important economic constraint to the production of both bulb and seed onion crops. Symptoms caused by IYSV may be confused with those caused by other fungal and bacterial pathogens and virus-specific, reliable, sensitive, and rapid detection methods would improve the diagnosis. Antiserum was produced to Escherichia coli-expressed nucleocapsid protein of IYSV and an indirect format of the enzyme-linked immunosorbent assay (ELISA) was developed. IYSV could be detected in onion tissue at dilutions of up to 1:1,000. An IYSV-specific primer pair was designed and used in a real-time reverse-transcription polymerase chain reaction (RT-PCR) assay for the rapid detection of IYSV. Compared with standard RT-PCR, real-time RT-PCR was more rapid and sensitive. A commercially available RNA extraction kit and a total nucleic acid extraction method were compared for the quality of the templates obtained for use in real-time RT-PCR and there was no difference in limits of detection. Availability of ELISA- and PCR-based rapid and sensitive detection methods would facilitate accurate virus diagnosis and aid in better understanding of the epidemiology of the disease and in development of management strategies.