Breeding for phytonutrient enhancement of potato

The potato is a vegetable that develops underground as a stem. It is a propagule in the sense that the potato itself is used as seed for the following crop. As a food it is a rich source of nutrients. All potatoes have carotenoids in the flesh which are xanthophylls. Of greatest interest are lutein and zeaxanthin, components of the human retina that must be obtained from foods for proper eye health. Potatoes grown outside the center of origin in the Andes of South America may contain from 50 to 350 micrograms zeaxanthin equivalents per 100 g FW. Potatoes developed by farmers in the Andes, especially the Papa Amarilla class of cultivars, may contain as much as 2,000 mu g per 100 g FW. Xanthophylls are fat soluble, have half-lives of several days in the human body, and are antioxidants that associate with membranes in the cell. Anthocyanins are radically different compounds conferring red to purple coloration to skin and flesh of potato. Potatoes with color of this type range from 1.5 mg cyanidin equivalents per 100 g FW, in colored skin but non-colored flesh types and up to 40 mg in colored skin, solidly colored flesh types. Potent antioxidants, anthocyanins are water soluble and have a half-life of several hours in the body. Some of the anthocyanins are strong anti-inflammatory agents. Potato is recognized as containing minerals, though never mentioned as a particularly rich source. A survey of advanced breeding lines and varieties at different growing locations indicates that different genotypes display a large range of iron content. Iron is the most problematic mineral from a dietary standpoint. Absorption from food is hindered by phytic acid and polyphenols, which are abundant in small grains and food legumes, while present in minute amounts in potato. The difficulty in absorption is countered further in the presence of vitamin C, which aids iron absorption. Potato is a substantial source of vitamin C and theoretically could be a principal component of a food matrix that provides highly absorbable iron.