DURUM WHEAT GENOME SCAN REVEALED TEN-THOUSAND YEAR EMPIRICAL SELECTION AND BREEDING EFFECTS

The durum wheat Svevo genome has bee n assembled to nearly completeness, more than 66k high confidence genes plus 8.4 Gb (82%) of repetitive elements were annotated and more than 928k sequence based molecular markers were projected onto the genome. By projecting more than 1,000 QTLs we identified the genomic regions enriched in QTLs for flowering time, plant height, grain size, spike fertility, response to rusts and grain quality. A higher QTL density was observed in the telomeric regions of chromosome groups 2, 6 and 7, consistently with the gene density distribution pattern. The durum wheat genome resource is being used to unravel the genetic diversity and ancestry of tetraploid wheat germplasm. Illumina 90K SNP array was used to genotype an extensive collection of more than 2,000 accessions covering the complete range of wild and cultivated emmer wheat, T. turgidum subspecies, durum landraces and cultivars from the domestication and cultivation areas. We applied both in silico chromosome painting and whole genome selective sweep analyses together with the genome wide QTLome distribution to describe the loci associated to the selection process. The transition from wild emmer to domesticated emmer was marked by selection sweeps in correspondence of QTLs for grain size, indicating that domesticat ed emmer, besides spike threshability, was selected also for increased yield. The transition from domesticated emmer to durum landraces was associated to major selective sweeps (Fst > 0.7 and XP-CLR > 50) overlapping with known QTL, mostly for grain size (18 sweeps on chromosomes 1A, 1B, 3B, 7A and 7B), grains per spike (five sweeps, particularly on chromosome 1B) and grain yellow pigment content (five sweeps). Additionally, the Svevo genome is being used as a genome reference for marker enrichment and positional cloning of a series of loci/QTLs of breeding relevance including CduB1, Sbm2, rust resistance, grain yield and root growth angle QTLs. For all of these cases, an update on how the availability of the durum wheat genome sequence help has been used in the process of fine mapping and marker development will be presented.