Abstract: Two-line hybrid rice, Liangyoupeijiu, is a landmark for super rice breeding in China National High-tech R&D Program. It has the largest planting area for years after the widely planted three-line hybrid Shanyou 63, and a significant impact in rice breeding area. Breeding practice in Liangyoupeijiu experienced a difficult and tortuous process of scientific research and production applications. Initially, the authors attempted CHA using a typical indica-japonica hybrid, Yayou 2. After failure of the attempt, the technical route was adjusted as: developing hybrid by partial-use of indica-japonica heterosis, and screening a plant ideotype suitable for ecological conditions in Changjiang-Huaihe region. The hybrid should have higher and stable seed setting rate, ultra-high yield, good grain quality, multiple resistances to disease, extensive adaptability, and safety for seed production as well. By analyzing key agronomic traits of hybrids, which used a lot of PTGMS lines as female, different ecological type lines as male, the authors determined the key female of Pei’ai 64S which was 1/4 relatives to javanica, and selected elite indica lines as male which belongs to the advantages cline and can avoid long growth period and higher plant of its F1, and screened the combinations adapting to the climate conditions in ChangJiang-Huaihe rice region. By screening a large number of combinations, the hybrid Liangyoupeijiu was obtained, which achieved genetic, morphological and functional “three excellent”, and the good grain quality, ultra-high yield, multiple resistances are gathered in one. Through studies on the hazardous high and low temperatures to fertility conversion and pollination of Pei’ai 64S, and frequency analysis on such temperatures in the various ecological regions, the authors put forward the suitable area for seed production and corresponding security heading date of parents. On the basis of the study on the plant temperature to Pei’ai 64S fertility conversion, the techniques for safeguarding the seed purity when confronted with low temperature weather in seed production were proposed. Through study on the biological characteristics and appropriate growth conditions of Liangyoupeijiu, the suitable planting areas and corresponding seeding and heading dates were proposed, the problems that may occur in the production were predicted and the corresponding preventive measures and solutions were proposed, and the cultivation techniques for increasing seed setting rate and its stability were developed. Supported by the research and application of the above techniques, Liangyoupeijiu was successfully cultivated in large-scale for years in Southern China. After reviewed the design of the research project, breeding theory and technical route, the tortuous processes for breeding, researching, developing and popularizing the hybrid, the authors discussed the significance of the achievement, put forward a complementary thinking of “fishgig-like” stem distribution for middle and base parts on rice plant ideotype, proposed the availability for selecting rice palatability by the complementation between indica and japonica types. To large-scale successfully cultivate a hybrid rice, prospective studies for the optimum growth conditions, the optimum planting area, the optimal cultivation measures, and a series of planting techniques to exert its advantages and avoid its disadvantages are very important.

Key words: Liangyoupeijiu, two-line hybrid rice, breeding, plant type, rice quality