Tracing the Origins of Domesticated Sunflower in Genes, Space, and Time

The search for domestication genes promises not only to reveal the specific changes contributing to crop traits but also to yield insight into the spatial and temporal dynamics of the evolutionary processes that led to the origin of domestication syndromes.  I will present several past and current studies that illustrate how domestication alleles have or will shed light on such complexity in the common sunflower, Helianthus annuus.  Our candidate gene studies of flowering time gene homologs have implicated a recent duplicate of the FLOWERING LOCUS T, HaFT1, as a domestication gene.  During early domestication, a selective sweep appears to have nearly fixed a frameshift allele of HaFT1, which produces a dominant negative effect on flowering time and disk diameter.  By surveying the haplotype diversity of HaFT1, several other domestication genes, and microsatellite markers across wild and landraces germplasm from North America and Mexico, our work has helped distinguish competing hypotheses raised in a recent controversy about the location of sunflower domestication centers.  Finally, to examine the pace and order of trait evolution during sunflower domestication, genome-wide ancient DNA studies of genes like HaFT1 that exhibit signatures of selective sweeps are underway.