Background: The genetic provenance of domesticated plants and the routes along which they were disseminated in prehistory have been a long-standing source of debate. Much of this debate has focused on identifying centers of origins for individual crops. However, many important crops show clear genetic signatures of multiple domestications, inconsistent with geographically circumscribed centers of origin. To better understand the genetic contributions of wild populations to domesticated barley, we compare single nucleotide polymorphism frequencies from 803 barley landraces to 277 accessions from wild populations. Results: We find that the genetic contribution of individual wild populations differs across the genome. Despite extensive human movement and admixture of barley landraces since domestication, individual landrace genomes indicate a pattern of shared ancestry with geographically proximate wild barley populations. This results in landraces with a mosaic of ancestry from multiple source populations rather than discrete centers of origin. We rule out recent introgression, suggesting that these contributions are ancient. The over-representation in landraces of genomic segments from local wild populations suggests that wild populations contributed locally adaptive variation to primitive varieties. Conclusions: This study increases our understanding of the evolutionary process associated with the transition from wild to domesticated barley. Our findings indicate that cultivated barley is comprised of multiple source populations with unequal contributions traceable across the genome. We detect putative adaptive variants and identify the wild progenitor conferring those variants.
Bibliographical noteFunding Information:
The authors thank Yaniv Brandvain, Justin Fay, Jeffrey Ross-Ibarra, Thomas Kono, and Justin Anderson for helpful comments on an earlier version of the manuscript. This work was performed using computing resources at the University of Minnesota Supercomputing Institute. We acknowledge funding from the US Department of Agriculture National Institute for Food and Agriculture USDA NIFA 2011-68002-30029 (to PLM) and University of Minnesota Doctoral Dissertation Fellowships (to AMP and ZF) 1Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108, USA. 2Current address, Bayer CropScience, 407 Davis Drive, Morrisville, NC 27560, USA. 3Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
© 2015 Poets et al.