Location: Emerging Pests and Pathogens Research
Project Number: 8062-22000-022-022-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2018
End Date: Aug 31, 2020
Research Objectives: 1. To develop improved detection methods for use with dormant tubers and soil/potting media infested with PMTV. 2. To validate the methods on field derived samples from known infested production areas.
Seed potato certification programs are the front line of defense against the introduction and spread of seed-borne diseases, most notably viruses and bacteria. Seed certification is primarily dependent upon visual inspection of the crop during the growing season and in winter grow outs of harvested tubers. Diseases that induce transient or no foliar symptoms pose a major challenge to visual inspections. If the pathogen is long-lived in the soil, potting media, or irrigation water it can further ex-acerbate the challenges to seed certification by providing a recurrent, but not easily detectible, inocu-lum reservoir in seed production areas. A modernization of seed certification procedures will require the development of reliable and economically viable diagnostics that can be applied to dormant tu-bers, soil, and water sources. This would allow an accurate assessment of seed lots prior to their dis-semination to other growers and an assessment of risk of infection prior to planting. Potato mop top virus (PMTV), a soil-borne virus, is transmitted by a soil dwelling protist, Spongo-spora subterranea, which itself is the causal agent of powdery scab on potatoes. PMTV induces no fo-liar symptoms on most potato cultivars, but causes internal tuber necrosis that render tubers unmar-ketable. Powdery scab causes surface lesions on tubers which decrease marketability and quality, and it causes galls on roots that decrease overall yield and plant vigor. The rapid penetration of these cou-pled pathogens into the U.S. potato industry, and particularly the seed industry, combined with inade-quate diagnostics and management methods, has created a critical and urgent need for research and engagement with affected producers and the allied industry. Our research efforts coordinate with seed certification programs and seek to develop and opti-mize diagnostics to detect PMTV in dormant tubers so that the harvested seed crop can be tested pri-or to being distributed to the commercial potato industry. Minimizing the dispersal of the pathogens in infected seed is a critical management strategy to prevent the infestation of other production fields. Additionally, diagnostic assays are being developed and optimized for detecting PMTV and Spongo-spora in soil and potting media so that growers and regulatory agencies can test fields and media prior to planting to minimize risk of harvesting an infected crop and perpetuating the disease in infested fields. Our overall goal is to better understand the scope and distribution of PMTV and its vector in the U.S. potato crop, improve on existing technologies for detection of all emerging PMTV strains, transfer the technologies to help build an infrastructure able to improve the capabilities and response of seed certification programs, and provide growers and regulators with timely information on best management practices.