Deciphering the Genetic Basis of Spikelet Meristem Identity in Barley

Inflorescence architecture is a major determinant of the components of final grain yield in the cereals. The inflorescence can take the form of a panicle (rice, sorghum, and maize) or a spike (wheat, barley and rye). Barley’s spike is composed of three spikelets (one central spikelet and two lateral spikelets) per rachis node that is a unique character of Hordeum species among Triticeae. Cultivated barley (Hordeum vulgare ssp. vulgare L.) produces either two-rowed (central spikelet fertile; lateral spikelets sterile) or six-rowed (complete fertility of the three spikelets) spikes. The six-rowed spike or lateral spikelet fertility is under the control of Six-rowed spike 1 (vrs1), vrs2, vrs3, vrs4 and Intermedium spike-c (int-c). However, the genetic basis of three-spikelet structure in a distichous manner was not fully elucidated yet. To address this, we will identify the gene responsible for the spikelet identity using zero-rowed spike 1 (zrs1) mutant derived from mutagenesis of wild barley (Hordeum vulgare ssp. spontaneum L.). The zrs1 mutant produces only two, presumably the lateral spikelets (sterile) per rachis node and shows severe abortion of florets in the central spikelet. We conducted phenotypic characterization and genetic mapping using genotyping-by-sequencing approach to understand the genetic basis of the zrs1 mutant.