On the diversity and origin of the barley complex agriocrithon inferred by iPBS transposon markers

The six-rowed barley with brittle rachis Hordeum agriocrithon A.E. angstrom berg is a diverse taxon connected with the evolution and domestication processes in the genus Hordeum. However, the origin and patterns of taxonomic divergence of this barley type is still hotly disputed. Here we utilized inter-primer binding site (iPBS) retrotransposon marker analysis to assess the genetic diversity of the complex taxonomic group H. agriocrithon in reference to the other two main barley taxa H. spontaneum K. Koch and H. vulgare L.. Based on selected iPBS primers, we demonstrated that the long-term process of natural evolution and human-driven domestication have influenced the dynamics of the TE fraction of the barley genome. iPBS markers reliably differentiated at molecular level the three main Hordeum taxa but also revealed genetic and phenotypic diversity patterns at within taxon level. Although H. agriocrithon can be considered as an autochthonous species due to its genetic divergence from H. spontaneum and H. vulgare, our results have shown that most of representatives of this taxon are of hybrid origin and hybridization events have shaped its highly heterogeneous genetic structure. Furthermore, our results strongly support the notion that H. spontaneum accessions are ancestors of the H. agriocrithon subgroup paradoxon and that the Caspian sea region is the likely place of initial cultivation and domestication of the six-rowed barley.