NON-TECHNICAL SUMMARY: This trans-disciplinary CAP project addresses three legislatively mandated areas; research in plant breeding and genetics of disease resistance; efforts to identify and address threats from pests and diseases; and efforts to improve production efficiency and profitability. It brings together researchers, extension professionals and seed certification programs from across the country to address the most important disease problem currently faced by the potato industry – vector borne tuber necrotic viruses. Potato mop top virus (PMTV) and some strains of potato virus Y (PVY) elicit necrosis in tubers, rendering the crop unmarketable. For the past decade we have been working under the guidance of a national advisory board, comprised of leading seed growers, affected ware potato growers, and representatives of large potato processing companies to prioritize our research activities. In this project we will: help growers reduce PVY and PMTV incidence in seed potatoes by developing high-throughput assays to detect these viruses in tubers; develop epidemiological models that include vector and virus population levels as inputs to model when/where disease will be most serious, and where control efforts are most warranted; screen the US potato genebank for new sources of resistance as well as develop markers for recently-mapped PVY and PMTV-resistance genes to facilitate breeding of resistant cultivars; and conduct economic and social analyses to assist industry and regulatory agencies in implementing changes to farm practices, certification programs, and national and state regulations. These activities will collectively reduce the impacts of tuber necrotic viruses to manageable levels for the entire potato supply chain.
OBJECTIVES: Necrotic potato viruses are the most important plant disease threat for the U.S. Potato Industry. Potato virus Y (PVY) is the number one cause of seed potato rejection in North America, it is transmitted non-persistently by aphids. Potato mop-top virus (PMTV), which is transmitted by the soil-borne pathogenic protist Spongospora subterranea, has spread to at least six seed potato producing states, and currently is present in 5% of seed potatoes from Maine. Since S. subterranea is common in peat-based potting mix, which is used to produce early generation seed potatoes, this pathogen has become widespread in North America. Current seed potato certification protocols are ineffective at managing these diseases, while pesticides are ineffective for managing both viruses and vectors listed above. We have made substantial progress in helping the industry manage these pathogens, but further work is needed (see progress report). Critical stakeholder needs are virus-resistant potato varieties, inexpensive high throughput testing of tubers for pathogens prior to planting, field management methods to reduce vector populations and pressure, social science information to aid in effectively implementing new technologies, and extension to teach farmers about these new management and testing methods.The potato industry views necrotic potato viruses as the primary threat to potato production in the United States. The long term goal of this project is to provide farmers with improved management strategies, and economic analysis tools to guide them in implementation of necrotic virus management strategies in order to reduce losses to necrotic viruses. The two necrotic viruses in this project, PVY and PMTV, infect other major crops and ornamental plants and are the type members of their genera, so knowledge gained through this work will improve general knowledge of plant virology as well as production of numerous specialty crops in the United States and throughout the world. PMTV is spread by the broad host range S. subterranea, which is also a pathogen, and which causes powdery scab on potato tubers and root galls on roots of many plant species.Therefore, our specific long term project goals are to:To translate high throughput detection of PVY and PMTV in dormant potato tubers, their vectors, and, for PMTV, in soil and potting mix, to plant diagnostic labs.To improve virus-vector management through development of epidemiological models and through research-based recommendations for potato production.To develop molecular markers for resistance genes against PVY and PMTV, and Ss; to clone at least one PVY resistance gene; and to understand virus impacts on the physiology of stored potatoes.To identify economic, or incentive barriers to effective disease management and to use this information to aid in industry adoption of improved management strategies and harmonized regulations.Outreach will occur at regional and national farmer education meetings, demonstration field plots, online via a project website hosted by Potatoes USA, and through online extension publications and videos. The majority of our project co-PDs and co-PIs are regular speakers at industry meetings and they will continue to provide outreach of knowledge generated by this project.
APPROACH: Objective 1: Multiplex high-throughput virus detection assays suitable for replacing the post-harvest grow-out test. Genomic analyses of virus and vector strains. The potato industry is demanding new tools to manage soil-borne necrotic viruses, in particular PMTV, in addition to the more traditional PVY. Due to the different biology of PMTV, new methods to test viruses in dormant tubers are needed. This tuber testing may also include PVY, but much work will be needed to select proper detection technologies and formats, adapt them for large-scale tuber testing, and develop appropriate sampling approaches so not to compromise the high quality of seed potato in the U.S. A complex approach is proposed in this proposal, including trials of new technologies, improved sampling methods, statistical analysis of the data, and a knowledge of the virus genetic diversity.Objective 2: Epidemiology models for virus vectors. Development of forecasting models for necrotic viruses. Several new on-farm approaches will be tested, including use of age-related resistance, cover crops, crop oils and insecticides, and protective mulches. These will be evaluated for their effectiveness and cost in various environments, and those selected as having superior results recommended to the producers. Epidemiology and forecasting models will be developed to predict risk in short- to medium-term. Virus tracking technologies will be developed to aid in epidemiological model development.Objective 3: Molecular markers for PMTV, and Spongospora subterranea resistance and a cloned PVY gene. Development of PMTV replicons to more quickly and accurately screen potato lines for virus resistance. Markers for PMTV resistance genes are not currently available. We will develop markers associated with resistance to PMTV, and also to the PMTV vector, S. subterranea, using segregating populations developed during the previous SCRI project and also newly created ones. PMTV is very unevenly distributed in infected plants, which makes screening populations challenging. To aid in marker development, we are developing a reporter replicons for PMTV to aid in marker development. This tool will also aid in development of epidemiological models for this virus. Objective 4: Identification of economic and social barriers to adoption of improved testing and management methods. We will aggressively “market” all our new tools to detect tuber necrotic viruses, new methods to manage the viruses on the farm, and new markers useful for breeding programs working on virus-resistant potato germplasm. The main measure of success of this proposed project will be the degree of adoption of the new tools developed by the researchers by the growers.
