Tissue Culture: How Modern Science is Saving Heirloom Potatoes

The nonprofit Seed Savers Exchange harnesses modern technology to preserve rare heirloom potatoes.

| Fall 2017

Few places showcase the outdoor beauty of northeastern Iowa as brilliantly as Heritage Farm, the 890-acre headquarters of Seed Savers Exchange located just outside Decorah, Iowa. The terrain boasts lush meadows and towering bluffs, bubbling trout streams and endangered livestock breeds, colorful apple orchards, and, of course, gardens displaying rare heirloom and open-pollinated plants.

So breathtaking is this working farm that you could easily miss some equally spectacular work that transpires indoors, tucked away in the basement of the administrative building. There, in a small section of the preservation department, you’ll see tools for cultivating plant life, but there are no garden trowels or soil. Instead, there’s a host of modern lab equipment: a glass-bead sterilizer and a laminar flow hood, autoclaves and test tubes — rows upon rows of test tubes, in fact. Sealed with colored stoppers and labeled with names like ‘Poorlander’ and ‘McIntyre Blue,’ these test tubes hold heirloom potato plants (Solanum tuberosum). The tiny plants belie a rich heritage deserving of preservation with a modern technique called tissue culture.

The technique involves growing new plants from small pieces of plant stem tissue in nutrient-filled test tubes under precisely controlled conditions. This process takes no small amount of time and resources. So what, then, is the benefit of preserving potatoes this way?

“Potato tissue culture is more secure than a collection of tubers alone,” says Tim Johnson, former head of preservation at Seed Savers Exchange (www.SeedSavers.org). “Once something is preserved in tissue culture, it can stay in tissue culture forever.”

Here’s why that’s so important: Unlike many other common garden vegetables, potatoes aren’t often grown from seed, but as clones. To grow a potato, you usually plant an existing potato, or at least a cutting from one. That “cloning” propagation process makes potatoes susceptible to soil-borne diseases that can reduce yield and ultimately destroy a cultivar.

“You plant a tuber, you get 10 new tubers, you eat nine tubers, and then you replant one the next year,” says Johnson. “Over time, though, the plants acquire viruses that are passed into the tubers, and eventually the viral load becomes so great that the plants start to lose their productivity. They get smaller and smaller until they don’t produce tubers anymore and are gone forever. Tissue culture allows us to preserve heirloom potatoes for future generations by ensuring that we don’t unnecessarily expose them to environmental pressures such as pests, unpredictable weather, and, especially, diseases.”

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