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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 F1 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 hm2 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. [ABSTRACT FROM AUTHOR]

Background China has been successful in breeding hybrid rice strains, but is now facing challenges to develop new hybrids with high-yielding potential, better grain quality, and tolerance to biotic and abiotic stresses. This paper reviews the most significant advances in hybrid rice breeding in China, and presents a recent study on fine-mapping quantitative trait loci (QTLs) for yield traits. Scope By exploiting new types of male sterility, hybrid rice production in China has become more diversified. The use of inter-subspecies crosses has made an additional contribution to broadening the genetic diversity of hybrid rice and played an important role in the breeding of super rice hybrids in China. With the development and application of indica-inclined and japonica-inclined parental lines, new rice hybrids with super high-yielding potential have been developed and are being grown on a large scale. DNA markers for subspecies differentiation have been identified and applied, and marker-assisted selection performed for the development of restorer lines carrying disease resistance genes. The genetic basis of heterosis in highly heterotic hybrids has been studied, but data from these studies are insufficient to draw sound conclusions. In a QTL study using stepwise residual heterozygous lines, two linked intervals harbouring QTLs for yield traits were resolved, one of which was delimited to a 125-kb region. Conclusions Advances in rice genomic research have shed new light on the genetic study and germplasm utilization in rice. Molecular marker-assisted selection is a powerful tool to increase breeding efficiency, but much work remains to be done before this technique can be extended from major genes to QTLs. [ABSTRACT FROM AUTHOR]