Crop Origin and Diversity

                                                     Alexander von Humboldt (1807)

Center of Origin and Center of Diversity

Alphonse de Candolle was the first to develop the subject of domesticated plant origins in his book, Origine des Plantes Cultiv�e, in 1883.  He compiled 249 species and listed their progenitors.  Nikolai I. Vavilov, a Russian scientist and pioneer of the plant genetic resources movement, (# Click on N.I. Vavilov) suggested the idea that many cultivated plants came from the same regions of the world called centers of origins.  The centers of origin were where these plants were domesticated and dispersed to other areas of the world.  For several of these crop species, the wild ancestors still exist in the center of origin.  However, today most scientists agree that centers of origin are not always equivalent to the centers of diversity because centers of diversity of different crops do not always coincide with centers centers of origins.  Often times centers of diversity do not always occupy a limited area and there might be secondary centers of diversity due to long history of continuous cultivation and introgression with wild relatives or between different races of a crop.

The number of described plant species worldwide is 250,000.  It is estimated that about 50,000 plant species still await discovery (# click on Classification of plants).  Humans throughout history have used about 7000 species of plants as food and of these, 200 have been domesticated as food crops.  Unfortunately, our dependence on the limited number of food plants continues to decrease historically.  Today, the world population depends on only three major staples: rice, wheat, and maize (three crops--wheat, rice, and maize--account for roughly 60 percent of the calories and 56 percent of the protein that humans consume directly from plants (#click on WRI Food Crops For Humanity).

After completing Unit I. Section C, please click on Section D. 

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