9707620 Kelley Sexual reproduction among plants and animals is thought to serve an important function which is to either reduce the incidence of disease, by producing genetically variable offspring which escape infection, or to repair genetic damage caused by deleterious mutations, which accumulate in organisms. The proposed research will investigate the importance of disease and mutation for offspring fitness, using a plant which is capable of both sexual and asexual reproduction. The fitness effects of viral disease and mutational damage will be measured in a field situation. Results obtained from this research will explain the evolutionary and ecological significance of genetic diversity in natural populations. They will provide a measure of the speed with which diseases can evolve increased virulence in response to particular host genotypes. These results will be directly relevant to understanding the origin of emerging diseases. Finally, experiments will yield an estimate of the consequences of genetic damage for natural populations. The consequences of environmental changes affecting mutation rates can be better understood as a result.
