Amy Charkowski, Vamsi Nalam, and Ana Cristina Fulladolsa, Colorado State University, Department of Agricultural Biology

Disease management is one of the major factors that affects how and where seed potatoes are produced in North America. Seed potato producers are located in northern regions, where cold winters control many diseases and insects that vector diseases and a complicated limited generation and certification system is used to manage some tuber-borne diseases. Two major categories of seed potato diseases limit production. The first includes vascular pathogens that predictably cause disease symptoms and that spread to other plants during production and many of these are effectively managed by the current seed potato production system. The second includes soil borne pathogens or vascular pathogens that are often latent in plants and the spread of these pathogens is unmanaged in our current system. Some of these pathogens, such as Spongospora, Helminthosporium, and Dickeya cause major losses and are difficult to effectively manage once they have infested the soil and water on a farm. Seed tuber production also has a major limitation in that seed tubers must be planted the following season. As a result, growers have essentially no option for other planting material when disease outbreaks occur and so growers are often faced with the decision of either planting diseased tubers or not planting their main cash crop. Breeding farms face similar dilemmas with frequent high disease incidence in important breeding lines, making it difficult to evaluate germplasm. 
True potato seed (TPS) production has the potential to limit spread of many diseases that currently plague the industry. For example, Potato virus Y, the main concern for seed potatoes, is not transmitted by TPS. Difficult to manage potting mix borne pathogens that can infect seed potatoes in the initial stages of seed tuber production, such as Spongospora and Colletotricum, are unlikely to spread in TPS. And, importantly, since TPS can be stored for several years, it is possible to maintain a healthy back-up supply of seed, something that cannot be done with our current system. However, other pathogens have the potential to emerge with production of true seed, such a PTSVd or strains of seed-borne bacterial pathogens. If true potato seed becomes more common in potato production, it is still likely that seed tubers will also still be used, and therefore growers will be faced with managing both tuber-borne and true seed-borne pathogens.
Many intertwined research and regulatory questions exist as TPS is developed. One initial need is identification of the pathogens of concern in potato TPS production and, following this, development of management methods for these pathogens. Another need is development of certification and phytosanitary protocols for import and export across state and national boundaries. Fortunately, tomato, which has a global seed market, provides many examples that will be useful for addressing these needs as the potato TPS system develops.