Genomic analysis of emmer wheat shows a complex history with two distinct domestic groups and evidence of differential hybridization with wild emmer from the western Fertile Crescent

Abstract

Triticum turgidum ssp. dicoccoides (wild emmer wheat) was one of the first plants that gave rise to domestic wheat forms in southwest Asia. The details of the domestication of emmer and its early dispersal routes out of southwest Asia remain elusive, especially with regard to its dispersal to the east. In this study, we combine whole genome data from a selection of specimens of modern wild T. turgidum ssp. dicoccoides and domestic T. turgidum ssp. dicoccum (emmer wheats) with a previously published 3,000 year old sample, to explore the phylogenetic relationships between wild and domestic populations of emmer, and especially the early dispersal routes south and eastwards to Africa and Asia, respectively. Our data confirm a marked differentiation between landraces from Europe, the Caucasus and Iran, and those from Africa, the Arabian Peninsula and India, the first group being more closely related to wild emmer from the northern and eastern Fertile Crescent. Gene flow is detected between wild emmer from the western Fertile Crescent and the second group of domestic emmer. These results support a dispersal route from southwest Asia to Africa, the Arabian Peninsula and India. We also observe a lower genetic variability in the wild emmer from the northern and eastern compared with that of the western Fertile Crescent. It is possible that the ancestors of domestic emmer that spread into Egypt still remain to be surveyed and analysed. Investigating the genetic content of ancient samples from Europe, the Caucasus or Iran would be very valuable to determine whether the two distinct types of germplasm arose during history or were already present during the early phases of dispersal.