Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: May 15, 2003
Publication Date: August 15, 2003
Citation: BROWN, C.R., CULLEY, D., YANG, C., NAVARRE, D.A. BREEDING POTATO WITH HIGH CAROTENOID CONTENT. PROCEEDINGS WASHINGTON STATE POTATO CONFERENCE, February 4-6, 2003, Moses Lake, WA. pp. 23-26. 2003. Interpretive Summary: Potatoes are generally recognized as providing a healthy high carbohydrate food. But potatoes also contain other healthy compounds. One group is the carotenoids that impart yellow to red colors to many plant parts and exist in white, yellow and sweet potato. Carotenoids are important in human nutrition and can function as antioxidants. They are also major constituents in the human retina. The carotenoids in potato are primarily xanthophylls, and are not pre-vitamin compounds. Studies have found that diets rich in carotenoid rich foods are associated with lower incidence of certain cancers and reduced incidence of heart disease. Our studies have found that we can develop potatoes through simple selection that are sixteen times higher amounts of total carotenoids. These potatoes look intensely yellow when cut open. They produce attractive processed products and taste very good. In addition we discovered that certain Peruvian varieties have carotenoid contents that are 40 times great than our white varieties. We believe that research leading to the release of new varieties with high carotenoid contents will benefit the potato industry. It will give consumers additional reasons to eat potatoes cooked at home or as processed snacks. Having a different kind of potato will diversify the options for potato growers and permit the processing companies to develop new products that they can advertise as having new healthful traits.
Technical Abstract: The carotenoids comprise a large group of compounds produced by plants. They usually are colored imparting yellow to red hues to various plant parts, including fruits and tubers or roots. The potato has carotenoids in the tuber. White potatoes have carotenoids as well as yellow and orange potatoes. However, the amounts vary over a great range. We developed a new technique to analyze the antioxidant properties of carotenoids. This involves composing a reaction mixture with cyclodextrin to mimic the membrane bound characteristics of the lipophilic carotenoids. We applied this to the Oxygen Radical Absorbance Capacity (ORAC) test. The ORAC consists of mixing the tuber extract with a fluorescing compound which loses its fluorogenic capacity as it is oxidized by a radical generating compound in the reaction mixture. The potato extract protects the fluorescing compound for a time. The ORAC is actually an area under the curve of fluorescence over a two hour period, during which time the fluorometer takes sixty measurements. The potato extract is calibrated against the antioxidant activity of alpha-tocopherol or vitamin E. We found that white flesh varieties grown on extensive acreages have total carotenoid levels of around 50 micrograms per 100 grams fresh weight. Standard yellow flesh varieties available to commercial growers range from 150 to 250 micrograms. Experimental clones developed in the USDA/ARS breeding program look intensely yellow and have total carotenoid contents of up to 800 micrograms. We found a significant correlation of total carotenoid content and ORAC. We also examined Peruvian cultivars that were grown in the Andes at high light intensities. The two highest levels were 1700 and 2000 micrograms. The ORAC obtained from these potatoes were five times higher than white fleshed potatoes. Both of these super high carotenoids were members of a highly specialized type of cultivated potato that has half the number of chromosomes of cultivated potato of the United States, Solanum goniocalyx and S. phureja. The development of high carotenoid potato varieties will permit exploitation of new product types and market niches, for potatoes that will be recognized as having high antioxidant properties.