Practice and Thinking on Rice Breeding for High Yield

Since the great increases of grain yield brought by the dwarf rice and hybrid rice breeding which benefited from using sd-1 gene and heterosis, rice high yield breeding seldom showed significant progress in the next successive two decades. The authors considered that, utilizing heterosis between indica and japonica varities would be an effective approach to increase grain yield further. By practice, a pure line cultivar, Nanjing 35 from a cross of japonica//indica/japonica, was bred and showed yield potential of 9 t/ha in 1970's. In the early 1990's, a typical indica-japonica hybrid, Yayou 2 showed its yield potential high as 10.5 t/ha. However, it failed to be commercialized for its qualifiedness of seed purity by using chemical agent in seed production, and sensitivity of seed set in F 1 to environment conditions. In the past decade, the authors released an intersubspeific hybrid, Liangyoupeijiu (Pei'ai 64S/9311), which exhibited grain yield high as 10-10.5 t/ha in wide climatic planting areas. The hybrid has been planted over 4.5 million ha, and was regarded as the pioneer of super hybrid rice. It would be the main approach for super hybrid rice breeding by using strong heterosis from indica-japonica F 1, together with plant ideotype, active physiological functions, and wide-range adaptability to ecological conditions as well.