Genetic Variation and Its Geographical Distribution in Aegilops caudata L.: Morphology, Hybrid Sterility and Gametocidal Genes

Abstract

Aegilops caudata L. is a diploid wild relative of wheat with the main distribution in the northeastern Mediterranean basin from Greece to northern Iraq. Two varieties are taxonomically described in this species based on spike morphology. In the present work, to elucidate the geographical differentiation pattern of the species, the geographical distribution of the two varieties was reviewed, 35 accessions derived from the entire distribution area were crossed with the four Tester lines, two varieties derived from their sympatric stands on the Aegean Islands were crossed with each other, and their F1, F2 and/or BC1F1 populations were examined. It became clear that the present distribution area of Ae. caudata can be divided into the western and eastern regions with the border in the mountains lying between West Anatolia and Central Anatolia: the western and eastern accessions are isolated not only geographically but also reproductively by hybrid sterility caused by gametocidal-like genes, and the morphology of var. typica is controlled by two different genotypes in the western and eastern regions. It was suggested that Ae. caudata occurred in the two isolated refuges during the maximum glacial period, the Aegean region and the western Levant or some sheltered habitats in the East Taurus/Zagros mountains arc, and that the latter population now occurs in the eastern region while the former now occupies the western region of the distribution.