Variation and geographical distribution of the genotypes controlling the diagnostic spike morphology of two varieties of Aegilops caudata l.

Aegilops caudata L. is an annual wild relative of wheat distributed over the northeastern Mediterranean basin. It consists of two taxonomic varieties, var. typica with awnless lateral spikelets and var.polyathera with awned lateral spikelets. To clarify the variation and the geographical distribution of the genotypes controlling the diagnostic spike morphology of the two taxonomic varieties, three crossing experiments were carried out. First, two varieties collected from nine sympatric populations in the Aegean islands were crossed reciprocally. All of the F1 hybrids were var. typica and the segregation ratio in the F2 generation was 3 typica: 1 polyathera. Secondly, 13 typica accessions collected from the entire distribution area of the variety were crossed with a common polyathera accession. The F1 hybrids involving eight typica accessions from Greece and West Anatolia were var. typica, while those involving five typica accessions from East Anatolia, Syria and Iraq were var. polyathera. Thirdly, the typica F1 hybrids between the Aegean and the Syrian typica accessions were backcrossed to the latter. Four of the seven BC1F1 plants obtained were var. typica, but the other three were var. polyathera. Based on these results, the following two conclusions were made. First, the awnless lateral spikelets characteristic of var. typica are due to two different genotypes: one is a dominant allele suppressing awn development on lateral spikelets and the other is a recessive allele(s) for awnless lateral spikelets with no dominant suppressor allele. Secondly, the former genotype occurs only in the western region of the distribution area of the species, while the latter occurs in the eastern region. The present results and the recent palaeopalynological evidence also suggested that var. polyathera, with more awns than var. typica, rapidly colonized Central Anatolia from the Levant or East Taurus/Zagros mountains arc after the last glacial period.