水稻雄性不育系及其保持系和恢复系,通称为杂交稻的“三系”。不育系在繁殖田里接受保持系的花粉,繁殖不育系种子。然后,不育系在制种田里接受恢复系的花粉,产生杂交稻种子。繁殖田和制种田的父本,即保持系和恢复系都是自花授粉,自行结实留种。所以在一般情况下,通过繁殖田和制种田两个生产环节,即可完成“三系”的繁育和配制杂交稻种子的全过程。实践证明,长期连续应用繁殖田和制种田里的“三系”种子,会使配制的杂交稻纯度下降,有 Male sterile lines of rice and their maintainer and restorer lines are commonly known as “three lines” of hybrid rice. Male sterile lines receive pollen from the maintainer line in breeding fields, breeding sterile line seeds. The CMS then receives the pollen from the restorer line in the field and produces hybrid rice seeds. Breeding fields and farming parents, that is, maintaining and restoring lines are self-pollination, their own strong seed. Therefore, under normal circumstances, the breeding process of “three lines” and the process of formulating hybrid rice seeds can be completed through the two production processes of breeding fields and farming systems. Practice has proved that long-term continuous application of breeding fields and the system of “three lines” of seeds, will make the hybrid rice purity decreased