Corn (Zea mays) Domestication: took place in Mesoamerica, around 5-6,000 B.C. Its ancestral origins are unknown, although primitive pod corn, Tripsacum, and teosinte are potential ancestors. Corn is a staple food in Latin America and the most valuable agricultural commodity in the world. It grown for human and animal food, oil, ethanol, and many other industrial purposes. Corn has extensive genotypic variability, due to a relatively active internal system for generating mutations known as transposable elements or transposons. Also, corn is monoecious and a natural outcrosser. This diversity is reflected in the numerous varieties of field corn, popcorn, sweet corn, and ornamental Indian corn available today. The advent of single-cross hybrid corn in the 1920s and 1930s revolutionized the corn breeding industry and vaulted corn productivity to unprecedented heights. Asgrow, Garst, Northrup King-Novartus, Pfizer-DeKalb, and Pioneer are the giants of the corn breeding industry. CIMMYT in Mexico is a leader in producing improved breeding germplasm for the developing world.
Rice (Oryza sativa) Domestication: took place in Southeast Asia, around 5,000 years ago. West African rice (O. glaberrima) and American wild rice (Zizania aquatica) were domesticated independently. Rice is the staple grain throughout most of the Tropics. The three recognized races are japonica, javanica, and indica rice. Rice cultivars are categorized as long-, medium-, or short-grained. Also, there are upland and paddy rice cultivars, the former being more important in Japan and Korea and the latter in tropical lowland cultivation. The introduction of dwarfing genes in the 1960s at IRRI in the Philippines and at CIAT in Colombia brought rice into the Green Revolution, and made several key Asian countries self-sufficient, or nearly so, in rice production.
Soybean (Glycine max) Domestication: took place in China, around 2,000 B.C. Soybean was relatively unknown outside of Asia until the early 20th Century, when its potential began to be recognized. It is now a high-value protein and oil crop and the U.S. is the world's leading exporter. Main production areas in the U.S. are the midwestern Corn Belt and the southeastern states. Soybeans are not an important crop in the West.
Sugarbeet (Beta vulgaris) Domestication: took place anciently, as the common vegetable beet. However, sugarbeets began to be grown and bred for their sugar only within the past 250 years, mostly for political or economic reasons.
Potato (Solanum tuberosum) and Tomato (Lycopersicon esculentum) Domestication: took place in the ancient Americas, with potato being domesticated in the Andes and tomato in Mesoamerica, though wild species of both are found in both areas. Whereas the tomato was reluctantly accepted in Europe, the potato rapidly rose to prominence as a major European crop after its 16th Century introduction. The legendary Irish Potato Famine of the mid-1800s led to the large-scale Irish exodus to America. This tragedy was due to potato monoculture and the introduction of a fungal disease, late blight (Phytophthora infestans), to which S. tuberosum has no natural genetic resistance. Irish peasant farmers had largely abandoned traditional crops such as oats in favor of the potato, which was higher-yielding and, until the appearance of the blight, had little or no natural pathogenic enemies in the British Isles. The famine was compounded by rampant human disease epidemics. Tomatoes became an important horticultural crop once the Europeans and European colonists to North America figured out that they were not poisonous.