Theories and Practices of Breeding Japonica Rice for Super High Yield

Advances and prospects in breeding japonica rice for super high yield were analyzed comprehensively in term of basic theory, breeding techniques and development of new varieties. The authors hold that an important way to increase yield potential of japonica rice in northern China is to develop and apply the super rice. New conventional varieties with super high yield, good quality and disease resistance have been developed and released. These have included Shennong 265, Shennong 606 and Jijing 88. With theories and methods for breeding japonica super rice, the goal is to create a new plant type and growth vigor through crossing indica and japonica subspecies. These two advantages are then consolidated through optimizing the combination of desirable traits via multiple crossing or backcrossing. In the project, this was established successfully. In contrast with conventional breeding for super rice, advances in breeding for hybrid japonica super rice is slower because of the limit of the northern climate and ecological conditions. The project sought to resolve the contradiction between heterosis and growth period, grain yield and quality.The problem of seed production is still an important challenge for breeding hybrid japonica super rice. Physiological and genetic problems in relevant japonica super rice were also discussed in this paper.