DISSERTATION RESEARCH: Evolutionary Genetics of Flowering Time Variation in Helianthus

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The research will investigate the genetic basis of an important developmental and reproductive trait, flowering time, and its responsiveness to an environmental cue, daylength, in annual sunflowers. Sunflowers exhibit an extraordinary diversity of daylength responses, and notably, changes in daylength response coincide with domestication, clinal variation in natural populations, and speciation. Conserved and novel aspects of gene and protein regulation in the developmental pathway that measures daylength will be assessed. Association of flowering time gene expression and daylength response will be measured in 1) domesticated sunflower, 2) wild populations of Helianthus annuus along a latitudinal cline, and 3) between a hybrid species and its two parent taxa. Whether sunflower copies of flowering time genes are located in genomic regions known to influence flowering will also be determined. Based on these results, the best candidate genes will be sequenced across several domesticated lines, Native American landraces, and wild populations of several sunflower species to ask whether and in which lineages these genes experienced positive selection. The project will identify genes involved in domestication, adaptation, and speciation, and connecting the evolutionary genetics underpinning a remarkably labile trait to a well-studied developmental pathway may provide new insights into the features of pathway architecture or gene regulation that facilitate evolution. Diagnostic tools for detecting sequence and expression variation of key flowering time genes will be developed for an important agricultural species. In addition, these resources will aid in conservation of a federally listed threatened species, and the project may identify genetic variation important for persistence of this species.