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Wild wheat Aegilops umbellulata Zhuk. (2n=2x=14, UU genome) is a valuable genetic resource for breeding of bread wheat (Triticum aestivum L. subsp. aestivum), which is one of the world’s most important food sources. The natural distribution of the Ae. umbellulata ranges from the Aegean islands, Anatolia, and the Middle East to Transcaucasus.

This species exhibits a wide genetic and phenotypic variations. Understanding the basis of these variations may provide valuable insights into the effective utilization of Ae. umbellulata in improving modern bread wheat varieties. As a step toward this goal, we analyzed the population structure of 199 accessions of Ae. umbellulata that largely cover the species natural range. All accessions were provided by the National BioResource Project-Wheat (Kyoto University, Japan).

The GRAS-Di®︎ sequencing reads were aligned to a chromosome-scale genome assembly of Ae. umbellulata (Abrouk et al., 2023, Sci Data 10: 739), and then 12,240 pruned single nucleotide polymorphisms (SNPs) were obtained. Population structure analysis based on the SNP genotypes showed that Ae. umbellulata has two genetically distinct lineages, namely UmbL1 and UmbL2.

The UmbL1 accessions spread in the region ranging from Turkey to northern Iraq, while the UmbL2 accessions spread in the western part of the Anatolian Peninsula, including the Aegean islands and Cyprus. Furthermore, the UmbL1 lineage was loosely divided into two sublineages: UmbL1e found in northern Iraq and UmbL1w found in central Turkey.

Within UmbL1, two groups of accessions with mixed genetic ancestries were found: one consisting of accessions with high percentages of the UmbL1e and UmbL1w genetic ancestries, and the other consisting of accessions with high percentages of the UmbL1w and UmbL2 genetic ancestries.

These groups, collectively named UmbL1x, might have originated through inter-lineage/sublineage hybridizations. Importantly, the population structure found in the present study was consistent with the one found in our previous study, which used an RNA-seq-based genotyping approach (Son et al. 2024, Sci Rep 14: 7437). These lineages/sublineages were not completely distinguished by morphology.

However, lineage-specific trends were observed in spike morphology: UmbL1w accessions have relatively long awns, and UmbL2 accessions have relatively short inter-spikelet rachis lengths.