9509074 DOEBLEY Closely related species can differ from one another by traits that best adapt each to the specific environment that it inhabits. How such adaptive traits evolved in nature is not well-understood. Many evolutionary geneticists subscribe to the view that the evolution of new adaptations typically involves changes at many genes, each with a small effect on an organism's appearance, or phenotype. Others have argued that one or two genes of large effect are sufficient to establish a new adaptation and that this is the more common mode of adaptive evolution in plants. Empirical studies germane to this debate are relatively few and inconclusive. The proposed research will investigate the genetics of adaptive evolution by analyzing the inheritance of adaptive characters that distinguish natural species of the genus Zea. The traits analyzed will include annual vs. perennial habit, rhizome formation, flowering date, degree of pigmentation in the leaf sheath, seed weight, and flower size and number. The inheritance of these traits will be determined by mapping the individual genes that control these traits to their positions on the chromosomes. By this means, it will be possible to determine the number of genes affecting each trait and the magnitudes of the effects of the individual genes. Overall, this study will provide a detailed picture of the genetic control of adaptively important traits from which one can infer the genetic basis of adaptive evolution in Zea. Because the genus Zea includes cultivated corn and because some of the traits to be studied are of potential agronomic importance, the proposed research can contribute to our understanding and improvement of corn.
