The Vrs1 gene was found to be highly expressed in the pistils of sterile lateral spikelets of two-row barley, showing that the VRS1 protein suppresses the fertility of florets in lateral spikelets. In addition, it was also found that the introduction of siRNA specific to the Vrs1 gene into two-row barley successfully restored the fertility of lateral spikelets and thus can increase the number of grains. The vrs1 gene derived from wheat was isolated for the first time, and the expression site of the gene was found to be specific to upper florets to be sterile in spikelets. Furthermore, it was confirmed that the introduction of siRNA specific to the wheat Vrs1 gene into wheat successfully increased the number of florets and the number of grains per spikelet, enabling provision of a method and an agent for increasing the number of grains per spikelet of wheat.
