Dissertation Research: Anthocyanin Biosynthesis and the Evolution of Red-Flowered Ipomoea

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Rausher0107172Natural populations of the tall morning glory (Ipomoea purpurea) are commonly infected by a fungal pathogen, Coleosporium ipomoeae. This plant has a single gene with two alleles that condition either complete resistance or susceptibility to infection. Both alleles are represented in natural populations of the tall morning glory, a pattern found in many wild plant species. This observation contradicts the intuitive prediction that an allele providing resistance against a harmful pathogen should approach a frequency of one. Hypotheses proposed to explain the resistance/susceptibility allele paradox suggest the net benefit of a resistance allele is mediated by inherent costs when the pathogen population is dynamic. This project will use field experiments to explore the potentially conditional benefits of the resistance allele in the tall morning glory. This work attempts to explain how natural selection may act to maintain genetic variation using the resistance/susceptibility allele paradox as a case study. In addition to contributing to the resolution of a fundamental issue in evolutionary biology, this work may also have applications to crop breeders who have historically incorporated resistance alleles from the wild progenitors of crop plants. As many countries become increasingly skeptical of transgenic crops, there is a renewed need to understand how natural selection acts on resistance alleles in natural populations, both to better utilize current resistant crops and to better conserve the natural resource that resistance alleles represent.