Root crops

David S. Seigler Department of Plant Biology University of Illinois Urbana, Illinois USA

Root Crops - Outline Botanical o roots, rhizomes, corms, etc. Domestication o mostly asexual reproduction o reduced toxicity o increased size Properties Nutritional + Water + Starch + Minerals, vitamins Preservation

Reading CHAPTER 7 IN THE TEXT

Introduction Root crops are underground parts of plants and include rhizomes, tubers, roots, stems, and leaves. Other than in the U.S., Western Europe and Japan, root crops are usually hand harvested.

Possibly domesticated before seed crops. Used by most hunter-gatherer societies. Domestication has not affected many of them significantly. Usually larger size. Sometimes lower toxicity.

Used in all cultures, but only major in a few: e.g., the potato in Europe, minor root crops in the Andes, and cassava in the lowland tropics. About as much grown in terms of tonnage as cereal grains, but much less nutritional value. The most important root crops are: cassava, potato and sweet potato.

Difficult to estimate production of many of these as they are consumed locally. Storage structures of plants. Often reproduced vegetatively. Mostly water. Some minerals. Starch. Used in most pre-agricultural cultures. Only in a few cultures have these become major food crops, mostly at high elevations in the tropics or in the wet lowland tropics. Crops from tubers and rhizomes

Root crops in market in Peru Courtesy Nancy Hikes

Mostly water and starch. Shipping involves shipment of water. Little protein or fats. Most root crops spoil easily when harvested.

Potatoes ( Solanum tuberosum) Potatoes (Solanaceae) and other related species were domesticated in Andean South America. Cultivated at least 4000 years ago. Potatoes will grow at elevations where few other crops can be cultivated. The early Spanish found potatoes from Colombia to Chile.

Potatoes in market in Wolfenbuettel, Germany

Potato field near Toluca, Mexico

Potato, Solanum tuberosum, Solanaceae

Either Sir Frances Drake or Sir Walter Raleigh brought back potatoes to England. The potato was enthusiastically received into Ireland. The climate was particularly suited to growing potatoes. By the 1840's the Irish ate unbelievable quantities of potatoes. In 1845, the potato blight (Phytophthora infestans) struck and wiped out the potato crop. Perhaps 1-2 million people died. At least another million came to the U.S. People obviously began to realize the hazard of depending too heavily on one crop.

Today potatoes are grown everywhere in upland tropical and in temperate parts of the world. Reproduced vegetatively. Burbank produced many new lines. Seeds often sterile. Solanum tuberosum cultivars are usually tetraploids. In the U.S. most of crop goes into potato chips and freeze dried instant mashed potatoes. These processes solve much of shipping weight problem.

Tuber about 80% water, about 20% starch, 2% protein. Toxicity of potatoes. Lenape line of chipping potatoes. Greened tubers can produce teratogenicity. In some areas of Bolivia, people practice geophagy to absorb the toxic materials from primitive lines of cultivated potatoes. Potatoes are often treated to prevent sprouting. Harvested potatoes are washed and stored cool. Sugar is converted to starch on storage.

Russia, Belarus, Ukraine, and Poland are major producers. In the U.S., Florida and California (winter) and Maine, California, Idaho (summer) are major producing areas. Newfoundland, Maritime Provinces, and Vancouver Island, B.C., in Canada.

Sweet potatoes (Ipomoea batatas, Convolvulaceae) Sweet potatoes are native to northwestern South America. They were taken very early to the South Pacific area and many considered them native there. Some postulated that sweet potatoes were taken from South America to the South Pacific by pre-Columbian voyagers.

Sweet potatoes, Ipomoea batatas, Convolvulaceae

Sweet potatoes have been found in South America as far back as years. They were cultivated by 2000 B.C. Some feel that they go back in the South Pacific as far as 1200 A.D. A hexaploid. Wild forms are not known with certainty. Origin complex.

The sweet potato is a true root. They are usually reproduced vegetatively using portions of the aerial stem. The roots contain about 2% protein. Lots of vitamin A.

In Japan, (especially) sweet potatoes are a major crop. They are used there to prepare starch, wine and alcohol. They are also widely fed to animals. China is easily the world's leading producer. Widely eaten in the southern U.S. Not eaten particularly in Europe.

Cassava (Manihot esculenta) Cassava (also known as manioc, mandioca, or yuca) is widely eaten. This plant is the major starchy food for more than 500 million people. Cassava is native to central South America and has been cultivated for thousands of years.

Cassava or yuca, Manihot esculenta, Euphorbiaceae

Peeling and washing cassava

Grinding and pressing cassava

Seiving the catevia and removal of nepe

Cooking the tortas

Tortas

Drying tortas and tortas in market

Griddles for cooking cassava go back at least 2000 years. However, since the crop developed in the lowland tropics where preservation is poor, it may go back much farther. Cassava contributes over 37% of the total calories consumed in Africa and 11% in Latin America. Little nutritional value other than starch. About 30% starch. Little protein. Doesn't keep well when harvested.

Cassava is toxic if not processed properly. The natives of South America had developed technology to remove the cyanide generating compounds. Sweet and bitter cultivars. Highly productive and little labor involved. Will keep for several months if left in ground. Reproduced vegetatively from stem cuttings.

Sweet types often boiled and fried. Bitter types often made into "tortas" or "farinha". Tapioca made from partially gelatinized cassava starch.

Yams or Ñame Not to be confused with the sweet potato (Convolvulaceae). Ignaime (French) or ñame (Spanish)... but probably originally from an African language. Yams are Dioscorea species and members of the Dioscoreaceae. Different species cultivated in Africa (where they were especially important), Asia, and the Americas. Probably tubers.

Dioscorea spp., true yams, Dioscoreaceae, female flowers

A yam, Dioscorea sp., Dioscoreaceae

Reproduction asexual. Many are poisonous and must be peeled and/or cooked to remove toxic principles. Yams relatively high in protein for root crops. In most places where yams were formerly cultivated, they have been replaced by sweet potatoes or cassava.

Taro and its relatives These are plants of the Araceae. Taro is Colocasia esculenta. Members of this family domesticated as root crops in both the Old and New World. Colocasia is native to Asia. A corm. About 30% starch, 3% sugar. Must be boiled to be eaten. A staple in the Polynesian area. In Hawaii, they use taro to make poi. Hawaiians used to eat lbs. per day.

Taro, Calocasia esculenta, Araceae, field in Madagascar

Taro, Calocasia esculenta, Araceae

Jicama, Pachyrrhizus erosus, Fabaceae

Minor Andean root crops A large number of these were domesticated in the Andes. Few (other than the potato) were used outside of the area. añu = Tropaeolum tuberosum arracacia = Arracacia xanthorrhiza oca = Oxalis tuberosa melloco = Ullucus tuberosus, Basellaceae, second only to potatoes in upland Peru. maca = Lepidium meyenii, Brassicaceae or Cruciferae. llacón = Polymnia sonchifolia, Asteraceae or Compositae.

Añu, Tropaeolum tuberosum, Tropaeolaceae Courtesy R. Norton

Añu, Tropaeolum tuberosum, Tropaeolaceae Courtesy Dr. Tim Johns

Arracacia, Arracacia xanthorhiza, Apiaceae Courtesy Nancy Hikes

Oca and quinoa in a Bolivian garden Courtesy Dr. Tim Johns

Oca, Oxalis tuberosa, Oxalidaceae Courtesy Dr. Tim Johns

Melloco, Ullucus tuberosus, Basellaceae Courtesy R. Norton

Maca, Lepidium meyenii, Brassicaceae or Cruciferae. Courtesy Dr. Tim Johns

Harvesting maca in Bolivia Courtesy Dr. Tim Johns

Llacón, Polymnia sonchifolia, Asteraceae or Compositae Courtesy Dr. Tim Johns