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Abstract
The study of domestication, the process by which wild species are selected for human consumption and use, can be used as a model for understanding the genetics of adaptation. Many economically important crops (e.g., sunflower and lettuce) are in the Asteraceae, the largest family of flowering plants. This family also includes a number of underutilized crops, which can serve as valuable resources for meeting the increasing food demands of the worlds growing population. Carthamus tinctorius L. (safflower) is an example of one such underutilized crop. Safflower is an attractive crop for further development, given that it is capable of growing in moisture-limited areas and is commercialized for its seed oils rich in unsaturated fatty acids. This dissertation has investigated the genetic diversity within and among wild, cultivated, and commercial safflowers. Additionally, the research presented here has characterized the genetic architecture of domestication traits in safflower and compared patterns of selection across crop and weeds species in the Cardueae. Population genetic analyses identified a significant decrease in allelic richness that occurred as a result of the safflower domestication bottleneck and identified useful sources for the future introgression of novel diversity from closely related, wild safflower species and parts of the safflower germplasm collection. The investigation of safflower genetic architecture revealed that, similar to the case in sunflower and unlike many other crops, the genetics of safflower domestication is complex. Moreover, comparative mapping results suggested that parallel trait transitions in these independent crop lineages may have been driven by parallel genotypic changes. Finally, molecular evolutionary analyses among safflower and its weedy relatives showed that Cardueae crop and weed species shared similar patterns of selection. Taken together, this dissertation has contributed to a body of knowledge on the genetics of adaptation, using safflower domestication as a model.