Mining the potential of VRS1-5 gene to raise barley grain yield

VRS1-5 genes determine spike row types during the early stages of spike development in barley (Hordeum vulgare), yet their functions for the determination of grain yield during the late stages of spike development are largely unknown. To assess the role of VRS1-5 genes in determining grain yield components, we sequenced VRS1-5 genes from 894 worldwide barley accessions and measured 19 spike morphology traits in four environments. Single nucleotide polymorphism SNP markers and gene marker-based haplotypes for VRS1-5 displayed close associations with spike morphology traits. We further developed a spatiote-temporal transcriptome atlas (255 samples) at 17 stages and five positions along the spike, that linked spike morphology to spikelet development and expression patterns of VRS1-5 genes. Phenotypic measurements demonstrated that mutations in VRS1-5 suppress the initiation of spikelet primordia and, trigger spikelet abortion by increasing cytokinin content and improving sensitivity of spikelet primordia to cytokinin. Our integrated results illustrate how breeding can globally alter spike morphology through diversity at the VRS1-5 genes, which show great potential in increasing barley grain yield.