Beginning of Essay
Genetic variation is the raw material for the plant breeder, who must often select from primitive and wild plants, including wild species, in search of new genes. The appearance of new diseases, new pests, or new virulent forms of disease causing organisms makes ....

Middle of Essay
.... diversity in plant crops. In certain geographical areas there has existed a rich source of variability in crop plants but the encroachment of civilization has reduced the natural variability inherent in primitive plant forms and related species of crop plants. Agricultural process, as a result of new breeding programs, has reduced rather than increased crop variability as improved cultivars, or varieties, are planted in wider and wider areas and old cultivars, which may contain valuable genes, are lost. Crop failures, which result in a smaller gene pool, have led to an increased awareness of the need to preserve genetic diversity in plants. ....