BLOOMINGTON, Ind. -- New genetic evidence presented by a team led by Indiana University biology doctoral graduate Benjamin Blackman confirms the eastern United States as the single geographic domestication site of modern sunflowers. Co-authors on the findings published this week in Proceedings of the National Academy of Sciences include Blackman's advisor, IU Distinguished Professor of Biology Loren H. Rieseberg, and four others from Rieseberg's lab, as well as collaborators from Universidad Nacional Autonoma de Mexico and the University of Cincinnati.
Through a comprehensive examination of the geographic diversity in three recently identified early domestication genes of Helianthus annuus, the researchers also reported finding no DNA evidence to support suggestions based on archaeological evidence that a second, independent domestication event had occurred in Mexico.
"Our results affirm that the eastern United States was an independent center of plant domestication and that all known living cultivated sunflowers shared a common origin there," Blackman said.
Controversy over the domestication of H. annuus began when sunflower seeds were found at pre-Columbian archaeological sites. It was proposed that, along with being domesticated in eastern North America, an independent sunflower domestication occurred in Mexico. Alternatively, sunflower may have been dispersed from eastern North America into Mexico through trade routes established before Spanish colonization.
This new work confirms domestication took place in eastern North America, probably in the Mississippi River Valley in the region of present day Arkansas.
The team analyzed the sequence diversity of three genes -- c4973, HaFT1, and HaGA2ox -- that had been identified as candidates for domestication genes, as well as the diversity of 12 neutral markers, and identified patterns of diversity in Mexican domesticated and wild sunflowers consistent with all other domesti
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