From Mediterranean wild grass to resilient Atlantic crop: tracing the evolution pathway of black oat ( Avena strigosa Schreb.)

Avena strigosa is a neglected diploid oat adapted to low-fertility environments, but its wild progenitor and domestication history remain unresolved because of taxonomic uncertainty among related wild oats. We combined DArTseq genotyping of 298 wild and cultivated Avena accessions with chromosome counts, population-structure analyses, phylogenetic reconstruction, EigenGWAS, and botanical and archaeobotanical evidence. The A. barbata-hirtula-lusitanica complex resolved into three differentiated lineages: tetraploid A. barbata, a diploid A. hirtula lineage associated with drier Mediterranean environments, and diploid A. lusitanica distributed along the humid Atlantic margin. Avena strigosa was genetically closest to, yet clearly separated from, A. lusitanica. This differentiation, together with domestication-related morphology and reduced diversity in the crop, supports a geographically localized domestication from A. lusitanica, possibly in Galicia. Avena strigosa comprised distinct Iberian and non-Iberian European gene pools, consistent with northward dispersal and adaptation after domestication. EigenGWAS identified highly differentiated loci in genes associated with environmental responses, including components of the CBF cold-acclimation network. These results clarify the evolution of diploid oats and identify wild and cultivated germplasm of value for conservation and breeding climate-resilient oats.