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- Multiregional origins of the domesticated tetraploid wheatsPublication . Oliveira, Hugo R.; Jacocks, Lauren; Czajkowska, Beata I.; Kennedy, Sandra L.; Brown, Terence A.We used genotyping-by-sequencing (GBS) to investigate the evolutionary history of domesticated tetraploid wheats. With a panel of 189 wild and domesticated wheats, we identified 1,172,469 single nucleotide polymorphisms (SNPs) with a read depth ≥3. Principal component analyses (PCAs) separated the Triticum turgidum and Triticum timopheevii accessions, as well as wild T. turgidum from the domesticated emmers and the naked wheats, showing that SNP typing by GBS is capable of providing robust information on the genetic relationships between wheat species and subspecies. The PCAs and a neighbour-joining analysis suggested that domesticated tetraploid wheats have closest affinity with wild emmers from the northern Fertile Crescent, consistent with the results of previous genetic studies on the origins of domesticated wheat. However, a more detailed examination of admixture and allele sharing between domesticates and different wild populations, along with genome-wide association studies (GWAS), showed that the domesticated tetraploid wheats have also received a substantial genetic input from wild emmers from the southern Levant. Taking account of archaeological evidence that tetraploid wheats were first cultivated in the southern Levant, we suggest that a pre-domesticated crop spread from this region to southeast Turkey and became mixed with a wild emmer population from the northern Fertile Crescent. Fixation of the domestication traits in this mixed population would account for the allele sharing and GWAS results that we report. We also propose that feralization of the component of the pre-domesticated population that did not acquire domestication traits has resulted in the modern wild population from southeast Turkey displaying features of both the domesticates and wild emmer from the southern Levant, and hence appearing to be the sole progenitor of domesticated tetraploids when the phylogenetic relationships are studied by methods that assume a treelike pattern of evolution.
- The evolutionary relationship between bere barley and other types of cultivated barleyPublication . Drosou, Konstantina; Craig, Hayley; Palmer, Karren; Kennedy, Sandra L.; Wishart, John; Oliveira, Hugo R.; Civáň, Peter; Martin, Peter; Brown, Terence A.We used genotyping-by-sequencing to investigate the evolutionary history of bere, the oldest barley variety still cultivated in Britain and possibly in all of Europe. With a panel of 203 wild and 401 cultivated barley accessions, including 35 samples identified as bere, we obtained filtered datasets comprising up to 1,946,469 single nucleotide polymorphisms (SNPs). The beres formed two genetically-distinct groups, the larger of which included beres from Orkney and the Scottish Western Isles, as well as varieties not identified as bere from the Faroe Islands. This group of beres was distinct from other British barleys, but had a close genetic affiliation with Scandinavian accessions. Although the data were partly compatible with the traditional view that bere was introduced to Scotland by the Vikings during the eighth century AD, the evidence as whole suggested that the bere and Scandinavian barleys are sister groups descended from a more distant common progenitor, possibly dating to the Bronze Age when hulled barleys first become common in northern Europe. More recently, there has been gene flow from these beres into Polish barleys, possibly following export of grain to the Baltic region during periods when Orkney was under Norwegian or Danish rule. A second, smaller group of beres, which included a traditional Welsh variety, was genetically distinct from the main group and probably represents a more recent introduction of barley from central Europe. Our results emphasize the uniqueness of bere barley and its importance as a heritage crop and a potential source of germplasm for breeding programmes.