Natural variation of morphological traits in wild wheat progenitor Aegilops tauschii Coss.

Aegilops tauschii Coss. (syn Ae. squarrosa L.) is a wild diploid wheat species. It has a wide natural species range in central Eurasia, spreading from northern Syria and Turkey to western China. Ae. tauschii is known as the D genome progenitor of hexaploid bread wheat. The genealogical and geographical structure of variation of morphological traits was analyzed using a diverse array of 205 sample accessions that represented the entire species range. In total, 27 traits, including anther and pistil shape and internode length, were examined in this study. Large-scale natural variation was found for all examined traits. Geographically, significant longitudinal clines were detected for anther size, internode length and spike size and shape. Anthers tended to be small in accessions from the eastern region. Internodes also tended to be short, whereas spikes tended to be long in accessions from the eastern region. Spikelet density per spike tended to be high in the eastern habitats. In the process of west-to-east dispersal, Ae. tauschii underwent extensive morphological, genetic and ecological diversification that produced the variation seen among today's natural populations.