A Robust Potato Tuber Tissue Collection Method to Investigate Potato Virus Y, Potato Mop-Top Virus, and Tobacco Rattle Virus Localization Patterns

Potato virus Y (PVY), potato mop-top virus (PMTV), potato virus S (PVS), and tobacco rattle virus (TRV) can be difficult to identify based on visual foliar symptoms. Using tuber samples collected from seven locations and 12 cultivars during 2017 to 2019, we developed a molecular assay using customized Whatman Flinders Technology Associates Plantsaver cards (FTA cards) and a reverse-transcription PCR (RT-PCR) for efficient sample collection and nucleic acid extraction. PMTV and PVY were detected more frequently on the stem end, TRV on the rose end, and PVS was evenly detected across the stem-end to rose-end axis of the tubers. Differences were seen in virus species localization within a tuber, thereby a composite of samples taken from multiple locations on a tuber improved virus detection. Regardless of sampling location on the tuber, tissue excised from the surface to 0.5 cm deep provided the best detection for all four viruses. For PVY, PMTV, and TRV, the proportion of tubers with viruses detected from field samples was highest at 100, 150, and 175 days after harvest, respectively. However, the probability of detecting PMTV and PVY 25 days after harvest was not different than the probability of detection at their peak detection times after harvest. The probability of TRV detection was lower at 25 days after harvest than at 175 days after harvest (<i>P</i> < 0.05).