Preservation and Utilization of Appalachian Crop Germ Plasm

Preservation and Utilization of Appalachian Crop Germ Plasm Elmer Gray Genetic Diversity, Erosion, and Preservation The history of agriculture is one of decreasing diversity and increasing specialization. Prior to its beginning some 10,000 years ago, man obtained food products from numerous wild plants. In the early stages of agricultural development, more than 3000 species of plants were domesticated for food production, but during the ensuing centuries, especially the present one, diversity diminished and specialization increased. Today, the plant agriculture which directly supplies 93% of our food is dependent upon 29 basic food crops for calories and protein and upon a similar number of vegetable and fruit crops for vitamins and minerals (Mitchell, 1983). Our highly specialized agriculture has reduced not only the number of crop species, but also the number of cultivars within the species. For example, in the United States more than half of the 1969 acreage of several crops—common bean, cotton, pea, potato, rice, and sweet potato—was planted with four or fewer cultivars per crop (Wilkes, 1983). Genetic diversity determines the boundaries of crop productivity and survival. Productivity is diminished when the genotype (variety of a plant) is unable to respond fully to the environmental potential and when the genotype fails to resist unfavorable environmental conditions. Examples of national disasters resulting from limited genetic variability have been documented for potato, coffee, wheat, and corn (Allaby, 1977). But despite these examples of potential problems or even disasters, the genetic diversity of many crop plants is under serious threat of destruction (Hawkes, 1983). Crop improvement through breeding depends upon the variability resulting from mutation—that genetic variability accumulated in wild species at their centers of origin and at other long-established habitats. Plant domestication resulted in the formation of cultivars, or particular varieties which growers maintain and transmit from one generation to the next. Thus, in earlier, more traditional agricultural practices, the genetic diversity essential for plant breeding was maintained in wild plants as well as in domesticated varieties. 35 The destruction ofwild habitat, plant domestication, plantbreeding procedures, and agricultural specialization have all contributed to the erosion of genetic reserves among crop plants. Moreover, the clearing of land for agricultural and industrial development fragments and isolates natural habitats, resulting in the disappearance of native plant species (Wolf, 1985 and 1987). The selection process involved in the development of different varieties and cultivars eliminates the less desirable genes and maintains more desirable ones. In the development of heirloom vegetables (varieties long associated with particular communities), less intensive selection over longer periods of time results in altered cultivated forms for a given family or community. On the other hand, variety development requires more intensive selection for genotypes that will perform over a wide geographic area. Development of such specialized varieties may involve the elimination of thousands of genotypes to find a few acceptable ones. Consequently (and paradoxically), success in plant breeding reduces the variability that made that success possible. To make matters worse, the practice of growing a single crop over extensive areas has contributed to the vulnerability of crops to diseases, pests, and adverse environments (Harlan, 1980). The high degree of specialization in modern agricultural production, marketing, processing, and consumption has, of course, resulted in specialized, narrow-based varieties. In fact, every major crop presently grown has a narrow geneticbase and is therefore vulnerable (Ford-Lloyd and Jackson, 1986). Partial Solutions To The Problem Serious efforts to conserve genetic resources began with the Russian geneticist and plant breeder, N.I. Vavilov. In 1926, he proposed that crop improvement be based upon wide genetic variation. To this end, he collected cultivated plants and their wild relatives from most parts of the world, to provide gene pools from which cultivars could be developed (Ford-Lloyd and Jackson, 1986). Since its inception, the Food and Agriculture Organization (FAO) of the United Nations has expressed interest in genetic resources. During the 1950s and 1960s, panels of experts identified crops and geographical areas where threats of genetic erosion were greatest. In 1974, international genetic conservation activities were initiated with the formation of the International Board for Plant Genetic Resources (IBPGR). This organization—jointly sponsored by the World Bank, FAO, and the United Nations...