The genome and gene editing system of sea barleygrass provide a novel platform for cereal domestication and stress tolerance studies

The tribe Triticeae provides important staple cereal crops and contains elite wild species with wide geneticdiversity and high tolerance to abiotic stresses. Sea barleygrass (Hordeum marinum Huds.), a wildTriticeae species, thrives in saline marshlands and is well known for its high tolerance to salinity and waterlogging. Here, a 3.82-Gb high-quality reference genome of sea barleygrass is assembled de novo, with 3.69Gb (96.8%) of its sequences anchored onto seven chromosomes. In total, 41 045 high-confidence (HC)genes are annotated by homology, de novo prediction, and transcriptome analysis. Phylogenetics, nonsynonymous/synonymous mutation ratios (Ka/Ks), and transcriptomic and functional analyses provide genetic evidence for the divergence in morphology and salt tolerance among sea barleygrass, barley, andwheat. The large variation in post-domestication genes (e.g. IPA1 and MOC1) may cause interspecies differences in plant morphology. The extremely high salt tolerance of sea barleygrass is mainly attributed tolow Na+ uptake and root-to-shoot translocation, which are mainly controlled by SOS1, HKT, and NHX transporters. Agrobacterium-mediated transformation and CRISPR/Cas9-mediated gene editing systems weredeveloped for sea barleygrass to promote its utilization for exploration and functional studies of hubgenes and for the genetic improvement of cereal crops.