MBE Advance Access published online on September 26, 2007
Molecular Biology and Evolution, doi:10.1093/molbev/msm192
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Research Article |
Molecular Diversity at 18 Loci in 321 Wild and 92 Domesticate Lines Reveal No Reduction of Nucleotide Diversity During Triticum monococcum (Einkorn) Domestication: Implications for the Origin of Agriculture
1 Institute of Botany III, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
2 Department of Field Crops, Faculty of Agriculture, University of Cukurova, 01330 Adana,Turkey
3 Regional Climate Group, Earth Sciences Centre, Göteborg University, Box 460, S-405 30, Göteborg, Sweden
4 Institute of Bioinformatics, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1,40225 Düsseldorf, Germany
5 Fondazione Parco Tecnologico Padano, Via Einstein – Localita Cascina Codazza, 26900, Lodi, Italy
6 Max Planck Institute for Plant Breeding Research, Department of Plant Breeding and Genetics, Carl-von-Linné-Weg 10, 50829 Köln, Germany
* author for correspondence: Benjamin Kilian, Max Planck Institute for Plant Breeding Research, Department of Plant Breeding and Genetics, Carl-von-Linné-Weg 10, 50829 Köln, Germany. Tel. + 49 221 5062 405; Fax: + 49 221 5062 413; E-mail: kilian{at}mpiz-koeln.mpg.de
Received for publication August 27, 2007. Accepted for publication September 6, 2007.
The diploid wheat Triticum monococcum L. (einkorn) was among the first crops domesticated by humans in the Fertile Crescent 10,000 years ago. During the last 5,000 years it was replaced by tetraploid and hexaploid wheats and largely forgotten by modern breeders. Einkorn germplasm is thus devoid of breeding bottlenecks and has therefore preserved in unfiltered form the full spectrum of genetic variation that was present during its domestication. We investigated haplotype variation among >12 million nucleotides sequenced at 18 loci across 321 wild and 92 domesticate T. monococcum lines. In contrast to previous studies of cereal domestication, we sampled hundreds of wild lines, rather than a few dozen. Unexpectedly, our broad sample of wild lines reveals that wild einkorn underwent a process of natural genetic differentiation, most likely an incipient speciation, prior to domestication. That natural differentiation was previously overlooked within wild einkorn, but it bears heavily upon inferences concerning the domestication process because it brought forth three genetically, and to some extent morphologically, distinct wild einkorn races that we designate here as 
, ß, and 
. Only one of those natural races, ß, was exploited by humans for domestication. Nucleotide diversity and haplotype diversity in domesticate einkorn is higher than in its wild sister group, the einkorn ß race, indicating that einkorn underwent no reduction of diversity during domestication. This is in contrast to findings from previous studies of domestication history among more intensely bred crop species. Taken together with archaeological findings from the Fertile Crescent, the data indicate that a specific wild einkorn race that arose without human intervention was subjected to multiple independent domestication events.
Key Words: evolution • molecular diversity • haplotypes • einkorn wheat • Fertile Crescent
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