Genetic dissection of the interactions between semi-dwarfing genes and and their effects on agronomic traits in a barley MAGIC population.

The introduction of semi-dwarf cereal crop varieties in the 1960s enabled extensive increases in global food production. Semi-dwarf barley cultivars have shorter stature and improved stress resistance, grain yield and quality than tall varieties. The major semi-dwarf genes, and , have been widely used in barley breeding programmes worldwide. In this study, we identified a novel allele in cv. Lockyer and investigated the effect of and and their interactions on plant height, flowering time and grain yield using a Multi-parent Advanced Generation Inter-cross (MAGIC) population generated from four elite barley cultivars. Allele-specific markers combined with Kompetitive Allele Specific Polymerase Chain Reaction (KASP) assays were used for fast and accurate screening of plants with different allele combinations. The results showed that the novel allele from cv. Lockyer had similar effects on plant growth and phenology as the known allele. The two semi-dwarf genes and had an additive effect for plant height with height reductions up to 27 cm. The gene triggered earlier flowering up to 6 days compared to WT and reduced the delay in flowering time caused by the gene. The two semi-dwarf genes boosted grain yields by 20% in the plants and up to 28% in plants with the two combined semi-dwarf genes. The results presented will benefit the development of higher-yielding and better-adapted barley cultivars.