Comparison of enzyme-linked immunosorbent assays and reverse transcription-polymerase chain reaction for the reliable detection of Australian grapevine viruses in two climates during three growing seasons

Background and Aims: Australian certification programs that provide high-health planting material depend on accurate virus detection methods. The reliability of enzyme-linked immunosorbent assays (ELISAs) and reverse transcription-polymerase chain reaction (RT-PCR) tests for virus detection was compared in Australian conditions. Methods and Results: Replicate trials were established in a hot climate and a cool climate with grapevines that were uninoculated or inoculated with Grapevine virus A, Grapevine fleck virus, Grapevine leafroll-associated virus (GLRaV)-2 and GLRaV-3. Grapevines were tested monthly for virus during 3 years. RT-PCR detected viruses more frequently than ELISA, and the reliability of both tests increased after 12 months and up to 3 years post-inoculation in both climates. Conclusions: Viruses may not be consistently detected until 12 months after an infection event. RT-PCR is more reliable than ELISA for virus detection during spring and summer. However, detection of viruses was rarely 100% efficient, and retesting of grapevines is recommended to improve the rate of detection. Significance of the Study: Validated diagnostic procedures were developed to improve the reliability of grapevine virus detection in Australia.