Submitted to: American Journal of Potato Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/29/2012
Publication Date: 2/21/2012
Citation: Whitworth, J.L., Hamm, P.B., Nolte, P. 2012. Distribution of Potato virus Y strains in tubers during the post-harvest period. American Journal of Potato Research. Volume 89:2:136-141. Interpretive Summary: Post-harvest testing of seed potato samples is done for Potato virus Y (PVY) in order to determine the amount for seed certification purposes. Tubers from Russet Burbank, Russet Norkotah, and Shepody, three widely grown cultivars were tested for PVYO, PVYN:O, and PVYNTN strains. ELISA and RT-PCR assays were used to test the tubers at the stem, middle, and bud areas of the tubers at dormancy break and then again after storage seventy eight days later. Results showed that ELISA underestimates the actual amount of tubers that are infected with PVY. Adding in the RT-PCR test results of the negative ELISA tubers gave an accurate picture of the distribution of virus in the tubers and the best post-harvest time to sample them. The N:O strain was unevenly distributed in the tubers and generally detected at a lower rate than the other two strains. Russet Norkotah and Russet Burbank had similar results with early testing having lower detection rates. Shepody was detected at about the same levels at the early and late samplings post-harvest. These results indicate that testing protocols should take into account that differences in detection rates due to virus strains and cultivars.
Technical Abstract: PVYO, PVYN:O, and PVYNTN infected tubers from Russet Burbank, Russet Norkotah, and Shepody were tested following storage, at the initiation of sprouting and then again at 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 ELISA and any negative tests were rerun using 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, the PVY N:O strain was unevenly distributed in some cultivars, but the PVYO and PVYNTN strains 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.