Abstract: A plant, the nuclear genome of which is transformed with a first foreign DNA sequence. The first foreign DNA sequence comprises a fertility-restorer DNA which encodes a first RNA, a protein or polypeptide that can inactivate a second RNA, protein or polypeptide in cells of the plant. The second RNA, protein or polypeptide is encoded by a sterility DNA in a second foreign DNA sequence in the plant's nuclear genome. Expression of the sterility DNA, in the absence of expression of the fertility-restorer DNA, would disturb significantly the metabolism, functioning and/or development of cells of the plant's flowers, particularly, the plant's reproductive organs, or cells of the plant's seeds or embryos in which the sterility DNA is selectively expressed, thereby rendering the plant male- or female-sterile. The first and second foreign DNA sequences also can encode suitable markers.