Despite the adverse climate for cereal breeding under the sufficient supply of cereals, breeding of hybrid rice was reestablished through the 1990s, and a series of new hybrids has been released and have shown a remarkable performance in Japan, the United States, and the temperate region in China,thus demonstrating an enormous potential for hybrid rice in the area. Superior experimental hybrids have been developed in Egypt and Korea. In that development, the private seed industry is playing a key role, as has been shown in India and China, while public institutes are still in a leading position in Egypt and Korea and for japonica hybrids in China. Even in Japan, where incentives for cereal production have been very low, a few private companies are trying to establish hybrid rice breeding in addition to Mitsui Chemicals Inc., which released hybrids to the market. Initiatives by the private sector seem to be decisively important in the development of hybrids. Strong demand for high rice grain quality is also common in the countries and the region being considered. The new series of hybrids is now much closer to the high quality standards than preceding ones. Hybrid rice technologies are not simple because of the coexistence of the two subspecies and the lack of heterogeneity in japonica types in temperate countries. Breeding methods are diversified because both indica and japonica types or intermediate types are planted in the countries. There is a strong preference for japonica-type rice except for the United States. The japonica haracteristic is also essential for cultivation in cooler climates, though adaptability to such climates is not strongly required in Egypt and the southern states of the U.S. While the broad diversity in the U.S. hybrid programs makes it easy to derive intersubspecific hybrids, which may account for the early success in high-yielding hybrids, the development of a heterotic genetic background is a central issue in the seed production system for japonica-type hybrids.
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