CRISPR/Cas9-Induced Dwarfism in Barley: Impacts on Yield-Related Traits and Root Architecture

Dwarf cereal cultivars were crucial for the Green Revolution. Dwarfed, lodging-resistant varieties remain essential today, as climate change brings more storms and downpours. In barley, the dwarfing gene HvDEP1 has been widely used in breeding. Although its pleiotropic effects on agronomic traits have been examined, previous studies relied on cultivars developed via random mutagenesis, which carry background mutations that may influence phenotypes. Moreover, its impact on root traits remains underexplored. We used CRISPR/Cas9 to generate precise HvDEP1 mutants and introduce dwarfism into the barley cultivar ‘Maythorpe.’ We assessed the effects on above-ground morphology, yield-related traits, root architecture, biomass via 13C labelling, and the root metabolome. HvDEP1 mutations significantly reduced plant height, straw, spike, and awn length, as well as thousand-grain weight. An in-frame mutant showed intermediate height, straw, and awn phenotypes. Belowground, in a root experiment restricted to knockout line #12, specific root length and the length of the finest (0–0.25 mm) roots were reduced, while total root length was lower but not significantly so; (p = 0.062). Root metabolomic profiling detected no genotype-associated differences. These results provide new insights into HvDEP1′s role in both shoot and root systems and demonstrate that precise CRISPR/Cas9-mediated editing can rapidly introduce dwarfism while revealing trade-offs in other agronomic traits.