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22 POTATO GROWER | APRIL 2023 DIGGIN' IN Potato Virus Initiative Developing Direct Tuber Testing Alternatives Waiting to know the level of potato virus Y (PVY) in a seed lot after harvest can be a game of patience. In some cas- es, the level of PVY may not be known until just a few months before planting. Having results as early as possible would be ideal for many reasons. Unfortunately, there are currently several time-consuming steps to gather certification information and assess the quality of the seed. The greatest hindrance is breaking dormancy and encouraging the seed to sprout and produce a plant several months before it normally would. Many of our seed potato certifica- tion agencies use winter grow-outs (WGOs) to determine the quality of seed destined for re-certification and commercial field production. Currently, the standard for a WGO is based on a 400-tuber sample collected from a given seed lot in September or October, soon after potato harvest, which gets treated with dormancy-breaking chemicals (e.g. Rindite) and sent for planting in a warm place like Hawaii or Florida. Leaves from plants emerging from these 400 tubers are collected in December-January and tested for the presence of potato viruses using labora- tory techniques or visually assessed for mosaic symptoms. Typically, the quality of a seed potato lot is certified by the end of January if Hawaii is used for the WGO. In Florida, potato growth may be slower, and the final evaluation may not be concluded until early March. Weather can often impact the emer- gence of seed in the various locations, which could further delay virus results. Seed potato growers have striven to speed up the decision-making process for seed certification and move it closer to the harvest time. Having informa- tion on the level of PVY in a seed lot as early as possible can help make field management and seed buying decisions. A 4-year project, "Potato Virus Initia- tive: Developing Solutions," is a feder- ally-funded Specialty Crop Research Initiative (SCRI), multi-state research and extension-based program. The mission is to develop sustainable system-based management strategies and decisions aids for tuber necrotic potato viruses. One part of the proj- ect is directly related to developing an alternative to the WGO by creating an assay applicable to direct tuber testing with the ultimate goal to create econom- ical and efficient means to manage the viruses. To avoid the need for shipping tubers to a remote, warm WGO location, cer- tification agencies would need to handle tubers directly in the lab: receive 400 tuber samples, subject them to treat- ments if needed, sample and process tuber tissue for analyses. It is a daunting task, which is quite different from the current methodology that focuses on sampling, processing, and testing of foliar samples. Novel approaches are needed to handle the U OF I | By Alex Karasev and Nora Olsen, University of Idaho