University of Idaho Plant Physiologist Mike Thornton and his team operate a potato research program at the Parma Research and Extension Center that focuses on evaluation of new potato varieties and development of cultural practices to optimize management of those varieties. The goal of the program is to select and help promote adoption of new potato varieties for the fresh and processing industries, with special emphasis on specialty varieties.
Selecting Specialty Varieties
Specialty potato varieties with unique combinations of skin and flesh color, shape, culinary quality and nutrient content occupy a small but increasingly important market niche. Idaho has become a major supplier of specialty potatoes to that market, and identifying new varieties with good agronomic and culinary qualities helps provide new marketing opportunities.
Field selection trials to identify new specialty varieties adapted to Idaho are conducted at Parma in cooperation with the Northwest Potato Variety Development Program (Tri-state). Tubers are evaluated at harvest for yield, size profile, shape, specific gravity and incidence of physiological disorders. A sample of tubers from each entry is placed into storage and evaluated for culinary quality after preparation by boiling, microwaving, baking and frying. The tubers are also evaluated for Vitamin C content, total antioxidants and glycoalkaloids, all in an effort to identify those with the best cooking and nutritional qualities.
The best performing lines from these trials are entered into the Western Regional Red/Specialty trials at six additional locations, where they undergo further evaluations for agronomic performance and more extensive tests of culinary quality by a group at Washington State University. A line that makes it through this series of tests is named and released to the industry for production and marketing. A recent example of a new variety to come through this program is Huckleberry Gold-a purple-skinned, yellow-flesh variety released in 2011 and evaluated under the line number A99326-1P/Y.
The most promising advanced lines from this program are placed in cultural management trials to evaluate the impact of seed spacing and fertilizer rates on yield, tuber size distribution, incidence of defects and economic returns. Information from this research is summarized in cultural management guides that are posted on the UI Potato Center and PVMI websites.
Improving the Appearance
Skin color and brightness are key attributes that have been shown to draw consumers to specialty potatoes. This project evaluates a wide range of in-season, storage and packing processes that potentially impact skin quality in specialty potatoes. For example, we have shown that several commercially available plant growth regulators can visibly increase skin color in red-skinned potato varieties, but seem to have no effect on yellow- and purple-skinned varieties. We also found that the timing of vine kill and harvest can impact the level of russeting and greying in purple-skinned varieties.
In cooperation with Nora Olsen and Phill Wharton, we have evaluated a number of post-harvest practices such as curing duration, holding temperature, vegetable waxes and common wash water disinfectants for impacts on skin color and appearance. In general, these practices had relatively little effect on skin color, although the vegetable waxes did darken skin color in some varieties. We are currently running additional studies to see how waxed potatoes hold up after packaging when exposed to high temperatures.
Other Research Projects
The need for more rapid adoption of new potato varieties has recently been heightened due to public debate about sustainability in agriculture. One of the best ways to meet consumer demands for more sustainable potato production practices is through adoption of new potato varieties with increased pest and stress resistance. However, relatively little research has been done to document the extent that inputs of water, fertilizer and pesticides can be reduced when producing new varieties.
We are working in cooperation with fellow University of Idaho scientists Jeff Stark (agronomy, variety development), Phill Wharton (pathology) and Paul Patterson (agricultural economics) on a project funded through a Specialty Crop Block Grant from the Idaho State Department of Agriculture to document the environmental and economic impacts of reduced pesticide use in six potato varieties. The goal is to use this information with large potato buyers to show how adoption of new potato varieties can help meet corporate sustainability initiatives.
Evaluation of potential new fresh and processing varieties for adaptability to southwest Idaho conditions have been part of the Northwest Potato Variety Development Program since the 1990s. Those trials continue today. The main goal of this research program is to identify lines with potential for the early fresh market or processing harvest window (late July to early August) and resistance to stress. The growing environment in this region seems to be particularly suited to causing the expression of dark-ends, and all variety trial entries are evaluated for this defect.
With such a diverse set of ongoing research trials, it turns out that we are harvesting potatoes from early August through late September every year. We enjoy having industry cooperators stop by to provide input on our program and to help evaluate new varieties. Contact Dr. Thornton at (208) 722-6701 or email him at miket@uidaho.edu.