Gene Recombination in Plant Breeding

Abstract

Plants differ in many ways. It may be safely generalized that no two plants are exactly alike, even though we may limit our observations to a single species. For an example, let us look at a field of corn. Upon casual examination we may be impressed with the similarity of the plants within the field. There is a certain constancy of features among the corn plants: the development of the stalk; the size, shape, and arrangement of the leaves on the stalk; the termination of the stalk in a tassel; the formation of ear shoots at nodes midway of the stalk; and many other developmental features. By these and other characteristics we recognize the corn plant and distinguish it from a plant of wheat, soybeans, or cotton. However, if we should compare two plants of corn in minute detail and make careful observations and quantitative measurements of the separate plant parts, we would find that individual plants differ in many respects. This would be the case even though the field was planted to a single-cross hybrid, which would be as nearly uniform genetically as we could obtain within a commercial field of corn. If we were to examine plants from a wide range of varieties of corn, we would expect to find even greater variations. There would be differences in maturity, height, seed coat color, endosperm color, sugar content of the kernel, presence of plant pigments, disease resistance, and many more features. Some of the differences could be observed visually; others would require comparisons of quantitative measurements. A correspondingly wide range of variability may be found within other species of cultivated crops.