The White Potato Back to Map Page Ireland Although the majority of the world is currently fed by three major food grains-wheat, corn, and rice-the fourth major food staple is the white potato. A freshly harvested potato contains almost 80% water and 17% starch; the remaining 3% is protein, and only 0.1% is fat. Potatoes are consumed fried, mashed, or baked. In addition to being an important food, potatoes are also the source of starch for the manufacture of adhesives and alcohol, including many vodkas. Today, Europe and the former Soviet Union produce 70% of the world potato crop, followed by China, Poland, and the United States The United States produces 21.7 million metric tons of potatoes annually, mainly in Idaho and Washington, which amounts to 4% of the world potato crop. The white potato, Solanum tuberosum, is an annual with alternate phylotaxy and pinnately compound leaves; its fruit is a berry. S. tuberosum is in the Solanaceae, a family of dicots composed of about 90 genera and almost 3,000 species. Members of the Solanaceae include the tomato (Lycopersicon esculentum); paprika, chilies, green peppers, and red peppers (all of the genus Capsicum); ornamentals such as petunia (Petunia sp.); the tobacco plant (Nicotiana); and the notoriously poisonous plants belladonna (Atropa belladonna) and jimson weed (Datura stramonium). The Solanaceae family is also commonly known as the deadly nightshade family because of its poisonous members. This family stigma caused many people to resist growing the potato as a human food, so it was first used for animal feed only. Typical Solanaceae flower The potato is a tuber, a modified underground stem that stores starch and fo         Starch grains in Solanum           tuberosum tuber cells rms at the tip of astolon. The tuber is the only edible part of the plant, and it should be cooked before being eaten because heat destroys the many toxic substances found on and just under its skin. The most abundant alkaloid is solanin, C45H73NO15, a poisonous glycoalkaloid that is found especially in the aerial portion of S. tuberosum as well as in the skin of the tuber. Alkaloids are a major class of natural products that have a physiological effect in other organisms. They characteristically contain carbon, hydrogen, nitrogen, and in many cases, oxygen. Because of their potent pharmacological effects, alkaloids are the basis for many drugs. The origins of S. tuberosum can be traced as far back as 8,000 years ago when the Incan civilization extending along the west coast of South America collected potatoes growing at elevations of about 12,000 feet. The potato was introduced to Europe about 1580 by Spanish colonists, who used it as a food source on their return voyages from the New World. But although S. tuberosum is native to the Andean highlands from Colombia to Chile, nowhere was the potato more readily accepted, established as a major crop, and relied upon than in               Drawing of Solanum tuberosum Ireland. The climate and soil in Ireland are ideal for growing the potato, and it dominated as a dietary staple for Irish peasants from the latter portion of the seventeenth century to the first half of the nineteenth century. S. tuberosum was so important to the Irish that historians link the Irish population increase from 1.5 million to over 8.5 million in 80 years (1760-1840) to the existence of a reliable food source. The potato was a blessing especially for the peasant, as even small plots of land could produce enough of the tuber to sustain a family. It is estimated that the average Irish adult consumed up to 12 pounds of potatoes every day. However, in August of 1845, the fungus Phytophthora infestans made its debut in Ireland, devastating the potato crops. This pathogen was the mark of the "Irish potato famine," also referred to as the "great potato blight." The fungus attacked leaves and stems, making photosynthesis impossible as the organs blackened and abscised. The fungus attacked the tuber not only underground, but even after harvest and in storage. As a result, over 1 million Irish people had died of starvation by 1849, and an additional 1.5 million emigrated to other countries, mainly the United States. Within the past 10 years, 140 years after P. infestans devastated the Irish potato crops, farmers in the United States and Canada report attacks on their crops by fungicide-resistant strains. Within the past nearly 20 years, the fungus has also been reported in Europe and the Middle and Far East. As a result of this potential threat, in March of 1996 the International Potato Center in Lima, Peru, called for a global initiative to combat the fungus Traditional propagation of the potato is accomplished by planting a section of the tuber with an "eye" (an undeveloped bud) from which a new plant will grow. However, new varieties of potato are now being produced from seed, and the potato has been one of the genetically engineered foods added to our diets since about 1994. In 1998, Monsanto, a biotechnology company based in Missouri, marketed a potato called "New Leaf Superior." It has been genetically modified to produce a protein in the leaves that is toxic to the Colorado potato beetle, a most destructive pest of potato crops. References, Websites, and Further Reading Fry, W. E., and Stephen B. Goodwin. 1997. Resurgence of the Irish potato famine fungus. BioScience 47(6):363-72. Levetin, Estelle, and Karen McMahon. 1999. Plants and society, 2d ed. New York: McGraw-Hill Companies, pp. 224-27. Simpson, B.B., and Molly C. Ogorzaly. 2001. Economic botany: Plants in our world, 3d ed. New York: McGraw-Hill Companies. BioScience On-line Article by Fry and Goodwin http://www.aibs.org/biosciencelibrary/vol47/jun97.potato.html BioScience On-line Library, The American Institute of Biological Sciences http://www.aibs.org/biosciencelibrary/ Homepage for The International Potato Center in Lima, Peru http://www.cipotato.org/ Potato," Microsoft® Encarta® Online Encyclopedia 2000. © 1997-2000, Microsoft Corporation. http://encarta.msn.com The World Potato Congress http://www.potatocongress.org/columns/may/pavlista.htm Related Reading in Stern, Introductory Plant Biology, 8th Edition Chapter 2: The Nature of Life Carbohydrates, pp. 22-23 Lipids, p. 23 Proteins, pp. 24-26 Chapter 6: Stems Specialized Stems, pp. 95-96 Stolons, Tubers, p. 97 Chapter 7: Leaves Leaf Arrangements and Types, pp. 107-8 Diagram of Leaf Arrangements and Types, Figure 7.4, p. 109 Abscission, pp. 121-22 Chapter 8: Flowers, Fruits, and Seeds Differences Between Dicots and Monocots, including Table 8.1, pp. 129-30 Structure of Flowers, pp. 129-32 Fruits, pp. 132-39 Seeds, pp. 143-45 Chapter 10: Plant Metabolism Photosynthesis, pp. 166-70 Chapter 14: Plant Propagation and Biotechnology Genetic Engineering or Recombinant DNA Technology, pp. 247-51 Chapter 19: Kingdom Fungi and Lichens Kingdom Fungi-The True Fungi, pp. 336-50 Chapter 23: Flowering Plants Angiosperms, pp. 417-21 Chapter 24: Flowering Plants and Civilization The Nightshade Family (Solanaceae), pp. 450-51