Dissertation Research: Population Genetics of a Plant Disease Resistance Gene: Cf-2 in Natural Populations of L. pimpinellifolium

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0073082Schaal & CaicedoPlant disease resistance genes, involved in the recognition of invading pathogens, have been a subject of intense research in the past decade. This has culminated in the identification of a handful of resistance genes, mostly in crop plants. However, little is known about the evolution of resistance genes in natural populations. This project will focus on the evolution of Cf-2, one of the few resistance genes to have been identified in a noncrop species. Allelic diversity of the Cf-2 gene in wild populations of Lycopersicon pimpinellifolium, a close relative of the tomato, will be surveyed to establish levels of within- and between-population diversity. This genetic variation will be analyzed with respect to the geneological relationships among Cf-2 alleles, geographical location, resistance phenotype, and the effects of natural selection. These analyses will reveal the microevolutionary processes that have shaped Cf-2's evolution.Plant resistance genes offer a unique opportunity to study how selection and other population-level processes affect an ecologically important trait at the molecular level. The study of adaptation at this level has traditionally been hindered by lack of knowledge of specific genes and their functions. Resistance genes thus emerge as ideal candidates to elucidate the evolutionary dynamics of molecular adaptation. Furthermore, knowledge of the mechanisms underlying resistance gene function and evolution is important for the continuing management of crop systems and the pests which threaten them.