Issue link: https://read.uberflip.com/i/1513787
Improving Our Understanding Of Potato Mop-Top Virus In The Northwest U.S. By Kylie Swisher Grimm, Richard Quick, Launa Cimrhakl, Max Feldman (USDA-Agricul- tural Research Service) and Mark Pavek (Washington State University) Potato mop-top virus is becoming an increasing global concern due to both yield and quality losses in potato. Tuber symptoms induced by Potato mop-top virus vary by cultivar, but consist of brown, corky, necrotic tissue that appear as flecks, arcs or large blemishes in the tuber flesh (Figure 1a). In some cultivars, necrotic arcs or blemishes are found on tuber surfaces (Figure 1b). Potato mop-top virus is trans- mitted to potato by the Spongospora subterranea pathogen which causes powdery scab lesions on tuber surfaces and galling and necrotic lesions on potato roots (Figure 1b and c). There are currently no known chemistries with effective control of the soil-borne vector or virus, rendering this disease complex and problematic for potato growers. In ad- dition, no commercial cultivars grown in the United States are known to have immunity to Potato mop-top virus. In theory, immunity can be obtained in two ways: resistance to the virus itself, or tolerance to symptom development. For growers focused on domestic markets, lack of tuber symptoms is sufficient at harvest. However, growers focused on international markets require complete immunity to Potato mop-top virus, as diagnostic laboratories in other countries often test for viral detection rather than simply assessing symptom occurrence. Virus detection in asymp- tomatic tubers (those lacking internal or external tuber symptoms) can therefore lead to lot rejections. Researchers at the USDA Temperate Tree Fruit and Vegetable Research Unit in Prosser, WA, have been work- ing to improve the general understanding of Potato mop- Kylie Swisher Grimm of the USDA-Agricultural Research Service in Prosser, WA, discusses Potato mop- top virus at the 2023 Washington State University field day in Othello. 34 POTATO GROWER | JANUARY 2024