It was discovered that Vrs1 gene was strongly expressed in the pistils of sterile lateral spikelets of two-row barley. Thus, it was clarified that VRS1 protein inhibits the ripening of florets in lateral spikelets. Further, it was clarified that, by introducing an siRNA specific to Vrs1 gene into two-row barley, the fertility of lateral spikelets can be restored and the grain-bearing number can be increased. Wheat-origin Vrs1 gene was isolated for the first time and it was clarified that the expression site of this gene is specific to upper florets that are sterile in spikelets. Furthermore, it was proved that, by introducing an siRNA specific to wheat Vrs1 gene into wheat, the floret number and grain-bearing number per spikelet can be increased. As a result, a method and a chemical for increasing the grain-bearing number per spikelet of wheat can be provided.
