No abstract

The domestication of emmer wheat (Triticum turgidum spp. dicoccoides, genomes BBAA) was one of the key events during the emergence of agriculture in southwestern Asia, and was a prerequisite for the evolution of durum and common wheat. Single- and multilocus genotypes based on restriction fragment length polymorphism at 131 loci were analyzed to describe the structure of populations of wild and domesticated emmer and to generate a picture of emmer domestication and its subsequent diffusion across Asia, Europe and Africa. Wild emmer consists of two populations, southern and northern, each further subdivided. Domesticated emmer mirrors the geographic subdivision of wild emmer into the northern and southern populations and also shows an additional structure in both regions. Gene flow between wild and domesticated emmer occurred across the entire area of wild emmer distribution. Emmer was likely domesticated in the Diyarbakir region in southeastern Turkey, which was followed by subsequent hybridization and introgression from wild to domesticated emmer in southern Levant. A less likely scenario is that emmer was domesticated independently in the Diyarbakir region and southern Levant, and the Levantine genepool was absorbed into the genepool of domesticated emmer diffusing from southeastern Turkey. Durum wheat is closely related to domesticated emmer in the eastern Mediterranean and likely originated there.

Polymorphism for deletions was investigated in 1027 lines of tetraploid and hexaploid wheat and 420 lines of wheat diploid ancestors. A total of 26 deletions originating during the evolution of polyploid wheat were discovered among 155 investigated loci. Wheat chromosomes were divided into a proximal, low-recombination interval containing 69 loci and a distal, high-recombination interval containing 86 loci. A total of 23 deletions involved loci in the distal, high-recombination interval and only 3 involved loci in the proximal, low-recombination interval. The rates of DNA loss differed by several orders of magnitude in the two intervals. The rate of diploidization of polyploid wheat by deletions was estimated and was shown to have proceeded faster in the distal, high-recombination interval than in the proximal, lowrecombination interval.