Knowing Your Roots

Blog 7

Potatoes, we love them, particularly at this time of year. Thanksgiving is close, and it just would not be the same without those creamy mashed potatoes to accompany your turkey and cranberries. Did you know that Wisconsin ranks 3rd in US potato production?  Did you know that the potatoes you are enjoying actually began life anywhere from 5-8 years before they got to your plate?  Probably not, but during the next few blog posts we would like to introduce you the exciting journey that your potato takes from a lab in Madison, to isolated farms in pristine Northwest Wisconsin and even a trip to Hawaii for a lucky few. This is the process needed to produce the disease-free seed tubers that potato growers must plant to meet all your culinary potato needs.  We hope these next blog posts will help illuminate this fascinating journey.

Potatoes are not grown from actual seeds, but come from daughter tubers (seed pieces) that carry all the traits of the mother plant. To be certain that plants are disease-free, true to variety and carry only the traits such as color, texture and taste that consumers desire, the journey starts in labs on the University of Wisconsin-Madison campus.  The Wisconsin Seed Potato Improvement Program, the first of its kind in the US, is funded by Wisconsin potato growers and directed  by Dr. Amy Charkowski of the UW-Department of Plant Pathology. Here, disease-free potato plants representing hundreds of varieties and characteristics are maintained. In the winter, tiny tissue slivers are grown into small plants in sterile test tubes. These tiny plants, the forerunners of your favorite baked or mashed potato, are then cut into even smaller pieces and grown into plantlets that have roots and leaves of their own.  Every spring, thousands of these plantlets are driven from Madison to an isolated UW Elite Seed farm in northern Wisconsin, close to Rhinelander. Once there, they are placed in protected hydroponic greenhouses, where they can grow over the summer and produce hundreds of pea to marble-sized mini-tubers, which represent the future of the potato industry. Over 400,000 mini-tubers are produced in Wisconsin using this method every year.  

To ensure that these mini-tubers are still true to type and disease-free and to increase numbers by 10-20 fold, the mini-tubers are then grown outside under carefully controlled conditions on the UW Elite Seed potato farm for an additional one or two years.  The potato lots are watched over daily by skilled inspectors and any plants that show even the slightest hint of impurity or disease are quickly removed. The results are fully-grown tubers in sufficient quantities for sale to the next tier of producers—the specialized certified seed potato growers who will tend them for the next 2-5 years until they are ready to be released for distribution to commercial potato growers throughout the US.

The specialized certified seed potato growers use the most advanced growing practices to increase the supply while maintaining varietal purity and low disease incidence tubers. These farms are typically located in isolated areas of northeastern Wisconsin where disease-carrying insects are rare. Each potential seed lot is carefully surveyed during the growing season by eagle-eyed inspectors who remove atypical or diseased plants. Finally, before the seed potatoes can be released to commercial growers, they must undergo one last rigorous challenge to be sure that they have zero or very low levels of a range of diseases that can infect potatoes and are true to varietal type. This is achieved by shipping a sample of each seed lot (the lucky ones!) to Hawaii where they can be grown during Wisconsin’s frigid winter, inspected and, if needed, undergo DNA analysis to determine that they meet the high standards required to become Wisconsin Certified Seed. Only then can they proudly wear the Blue Tag that certifies that they are Wisconsin Certified Seed that is ready for planting on any potato farm or home garden in North America.

The science that underpins this whole process is ongoing as new research is occurring daily to advance and update all aspects of the program with state-of–the-art technology.  In the next few blog posts, you will learn about some of the research programs being conducted at the University of Wisconsin-Madison to enhance Certified Seed production.  You will read posts directly from graduate students doing innovative research and exploring new approaches to keep the Wisconsin Seed Potato Improvement Program on the cutting edge and ensure that the potatoes that arrive on your plate this holiday season are as tasty and nutritious as always.

For more information on the Wisconsin Seed Potato Improvement Association visit: (

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