A small interfering RNA (siRNA) can be custom-produced in plant cells when a transgene comprising an inverted-repeat sequence is used to form the corresponding double-stranded (ds)RNA. This siRNA induces methylation of the homologous DNA through the RNA-directed DNA methylation (RdDM) pathway. As methylation of the promoter region causes transcriptional gene silencing (TGS), dsRNA for the promoter sequence of a gene can induce TGS of the gene, accompanied by modification of chromatin. Such epigenetic variation provides a novel technique to induce silencing of a target gene. Furthermore, once epigenetic variation has occurred, the siRNA need not be present to maintain the stable repression of transcription even in the subsequent generation. Thus, the induction of epigenetic changes is a potentially new plant-breeding technology to improve crops.