Hybrid rice has contributed greatly to the self-sufficiency of food supply in China. To meet the future demand for rice production, a national program on super rice breeding was established in China in 1996. The corresponding targets, breeding strategies and most significant advances are reviewed in this paper. New plant type models have been modified to adjust to various rice growing regions. In recognition of the importance of applying parents with intermediate subspecies differentiation in increasing F 1 yield, medium type parental lines were selected from populations derived from inter-subspecies crosses with the assistance of DNA markers for subspecies differentiation. Results also indicate that a substantial increase of biomass is the basis for further enhancement of the grain yield potential, and amelioration of leaf characteristics is helpful in increasing the photosynthetic rate. Thirty-four super hybrid rice varieties have been released commercially, growing in a total area of 13.5 million hm 2 and producing 6.7 thousand million kg more rice in 1998-2005. Although remarkable progress has been made in super hybrid rice breeding in China, selections on the root system and integration of more biotechnological tools remain a great challenge.

Heterosis is a heterozygous trait, depending on the genetic diversity of both parents. An approach to tag the heterosis trait with a molecular marker should be different from any other approaches for homozygous traits. To achieve this objective, it is necessary to identify the genetic diversity related to heterosis between both parents. This part of genetic diversity should be closely related to the parental combining ability, which is the most important factor for the performance of the hybrids. Based on the principle of parental combining ability, the simple sequence repeat (SSR) markers favorable and unfavorable to heterosis were identified in the previous study. In the present study, using these markers, two restorer lines with a very high combining ability, MGR44 and MGR45, were developed from the elite restorer line, Minhui63. In these two lines the favorable alleles were maintained while the unfavorable alleles were removed, resulting in the obvious increase of both the general combining ability (GCA) and special combining ability (SCA). Also, the spike density and 1000-grain weight traits were enhanced as compared with Minhui63. These results indicate that the previously selected molecular markers are very useful for hybrid rice breeding programs. Also, it was confirmed that the method described in our previous report is suitable and effective for screening molecular markers for hybrid rice breeding.

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