Multi-year evaluations of an FTA card-based detection protocol for four vector-borne viruses affecting potato.

To reduce reliance on time consuming post-harvest seed potato grow-outs, a Whatman Plantsaver FTA® card-based pathogen detection protocol based on dormant tubers was developed for four potato viruses. Viruses tested included potato virus Y (PVY), potato virus S (PVS), potato mop top virus (PMTV), and tobacco rattle virus (TRV). Viruses were also detected from potato tubers, sprouts, and leaves using different experimental test methods and sample collection timings (Harvest-FTA, Storage-FTA, Sprouting-FTA, Sprout-ELISA, and Sprout-RPA, Leaf-RPA, Leaf-ELISA). When compared to the Leaf-ELISA, accuracy of the Harvest-FTA was 92.9% (PVY) and 93.8% (PVS) and test results were available 90-days earlier than Leaf-ELISA. Results from the Leaf-ELISA for PMTV and Leaf-FTA for TRV grossly under report detection of these two viruses compared to results obtained using multiple tuber and sprout test methods (Harvest-FTA, Storage-FTA, Sprouting-FTA, Sprout-ELISA, and Sprout-RPA). In 2020, an on-farm collaboration resulted in field implementation of the FTA card-based tuber test for detecting PVY, PMTV, and TRV from eight seed lots. Accuracy, sensitivity, and specificity for detecting PVY from these eight seed lots using the Farm-FTA Test Method were 89%, 92%, and 87%, respectively, and the results were provided approximately three months earlier than the official results from the state seed potato certification programs. Cost analysis of the FTA card-based detection protocols showed that this approach reduced testing costs for multiple pathogens and allowed growers to use a single sampling pipeline to measure and manage multiple pathogen risks at lower costs.