The wood of the trunk is used in light construction. Furthermore, the buriti palm thrives in Amazonian swamps of little use for intensive agriculture (Schultes, 1979).
Relatives of commercial species must continuously be crossbred with these species to improve crop yield, nutritional quality, durability, responsiveness to different soils and climates, and resistance to pests and diseases (IUCN, 1980). Since many of the world’s most important crop species originated in the tropics, we must look to the equatorial regions for wild or semidomesticated relatives of commercial species to maintain or improve our crops.
A barley plant from Ethiopia has already provided a gene that protects a $160-million barley crop in California from the lethal yellow dwarf virus. A wild relative discovered by Iltis in the Peruvian Andes has increased the sugar content of the domestic tomato which has resulted in an increased commercial value estimated at $5 to $8 million per year (Witt, 1985; see also Iltis, Chapter 10 of this volume). In fact, tomatoes are one of the world’s most important crops, yet they could not be grown commercially in the United States without the genes provided by wild relatives (Harlan, 1984). Rice grown in Asia is protected from the four main rice diseases by genes provided by a single wild species from India. In both Africa and India, yields of cassava—one of the most important crops throughout the tropics—have been increased up to 18 times because of the disease resistance provided by genes from wild Brazilian cassava. Disease resistance provided by wild Asian species of sugarcane have saved the sugarcane industry in the southeastern United States from total collapse (Prescott-Allen and Prescott-Allen, 1983). Perennial corn, discovered by Guzmán in Mexico in 1977, has proven to be immune or resistant to the seven major diseases of domesticated corn (Witt, 1985).
Although the use of wild and semidomesticated relatives is already extensive, it will undoubtedly increase in the near future because of the wider availability of these plants and the growing documentation of their potential utility (Frankel, 1983; Prescott-Allen and Prescott-Allen, 1983). Rapid advances in genetic engineering will also provide greater access to certain gene pools, which can now only be taken advantage of with special techniques (Frankel, 1983).
Following are some good examples of the types of plants that may prove useful for future breeding purposes:
Coffee (Coffea spp.; family Rubiaceae) is a mainstay of the economy of several tropical countries, yet it is rather susceptible to certain fungal diseases. Although Africa is home to most commercial species (particularly C. arabica from Ethiopia), the island of Madagascar has approximately 50 wild species of Coffea. Some of these species may prove important for commercial breeding not only for their potential resistance to fungal infections but also because they produce beans with little or no caffeine (Guillaumet, 1984; Plotkin et al., 1985).
Two wild species of potatoes (Solanum spp.; family Solanaceae) have leaves that produce a sticky substance that traps predatory insects, which subsequently