Distribution of Potato virus Y Strains in Tubers during the Post-Harvest Period

Russet Burbank, Russet Norkotah, and Shepody tubers infected with Potato virus Y strains (PVY O , PVY N:O , PVY NTN ) were tested from storage at 4°C at the initiation of sprouting and then the same tubers were tested again from storage at 4°C seventy eight days later. Samples were taken from eyes in the stem, middle, and bud (distal end) areas of the tubers. Testing of the samples was done with an enzyme-linked immunosorbent assay (ELISA) and negative samples were retested using reverse transcription-polymerase chain reactions (RT-PCR). The ELISA alone and the ELISA+PCR combined results were evaluated for each of the strains, sample locations, sample time, and cultivar. Results show that ELISA underestimated the actual percentage of tubers with virus. When test results were combined to show a more accurate percentage, PVY N:O was unevenly distributed in some cultivars, but PVY O and PVY NTN were evenly distributed 78 days after initial sprouting. Results show that protocols for PVY post-harvest testing used by state seed certification agencies should be written to specify the amount of time needed before sampling and that specific protocols may be needed based on cultivar in order to accurately detect PVY in tuber samples.