Collection Details: The Cereal Crop Wild Relatives (Triticeae) collection comprises 935 accessions, consisting of 847 wild and 88 unadapted cultivated entries. Of the 847 wild accessions, 825 were stabilised as a Single Seed Descent for downstream genomic applications.
The wild Triticeae species in this collection originate mainly from the Mediterranean Basin, West and Central Asia, and parts of Eastern Europe. Main native regions include the Fertile Crescent, which covers modern-day Turkey, Iran, Iraq, Syria, Jordan, Lebanon, and Israel, recognized as centres of origin and diversity for many Aegilops and Triticum species. Other native habitats extend into the Caucasus and Central Asia (modern day Armenia, Azerbaijan, Georgia), North Africa (Egypt), and parts of Southern and Eastern Europe (modern day Greece, Bulgaria, and Romania).
The collection comprises 57 species with varying ploidy levels. The distribution of these levels among species shows significant variation within and across species, emphasising their complex evolutionary backgrounds. Most Aegilops species are tetraploid (x=28), including Ae. bicornis, Ae. biuncialis, Ae. columnaris, and Ae. crassa, indicating widespread polyploidization within the species. However, several diploid species such as Ae. caudata, comosa, mutica, speltoides, and tauschii represent distinct ancestral lineages with important genomic contributions to cultivated wheat. Notably, Ae. vavilovii, Ae. juvenalis, and Ae. Crassa, also present in hexaploidy form, demonstrates even more advanced polyploidy events. Similarly, Triticum species cover all major ploidy levels, from diploid progenitors like T. urartu and T. boeoticum to tetraploids such as T. dicoccoides, durum, and carthlicum, and hexaploids including T. compactum, spelta, and zhukovskyi, each reflecting specific hybridization histories involving the A, B, and D genomes.
The germplasm can also be classified according to the Gene-Pool Concept based on the species relatedness to wheat and barley. GP1 includes the modern as well as the unadapted form of the domesticated crop. GP2 includes species that can cross with the crop, but with more difficulty. In the wheat collection, GP2 species include speltoides, Ae. longissima, Ae. mutica, T. timopheevii, T. dicoccum, T. monococcum, and T. zhukovskyi.
Other species show diverse genomic structures as well. Thinopyrum elongatum exhibits a remarkable range of ploidy—from diploid to decaploid—while Thinopyrum intermedium and T. bessarabicum represent hexaploid and diploid forms, respectively. The genus Eremopyron includes multiple species with variable or unresolved ploidy, indicating a less-defined evolutionary pathway. In contrast, diploid taxa such as Hordeum chilense, H. vulgare, Dasypyrum villosum, and Henradia persica maintain more conserved chromosome numbers and likely serve as basal lineages in Triticeae evolution. This ploidy spectrum across wild and domesticated relatives underscores the dynamic nature of polyploidization in grass evolution and its fundamental role in shaping modern small-grain cereal diversity.