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What is Hybrid Rice?

Hybrid rice is rice that has been created by crossing two different parental strains. Such crosses generally result in an F1 generation that is more robust than either of the parental strains. The improved qualities of the F1 generation is referred to as "hybrid vigour" or "heterosis". The hybrid vigour may result in superior agronomic qualities such as higher yield, stronger resistance to diseases, more efficient use of soil nutrients, and better weed control. Hybrid vigour and other superior qualities arising from crossing genetically different plants has been well known and used by traditional crop breeders for decades.

In the past, the production of hybrid rice strains was limited by rice's inherent propensity to self-pollinate. In 1974, Chinese scientists overcame this when they developed the first generation of hybrid rice using a three-line hybrid system based on cytoplasmic male sterile (CMS) lines and hybrid combinations. In 1996, an even more efficient second generation of hybrid rice was developed based on photoperiod-sensitive genetic male sterility (PGMS) lines.

Traditional rice production (i.e., non hybrid rice) relies on rice varieties. A rice variety is a rice line that is a group of rice plants distiguished by common characteristics of significance to agriculture and often has been assigned a commercial name. When rice is produced from a variety, a single line is planted and it fertilizes by self-pollination. When a rice variety is reproduced, it retains its distiguishing characteristics, and farmers can keep seeds for replanting next season.

In contrast, hybrid rice is the product of a cross between two distinct rice lines, and due to the difficulty of making hybrids, they are generally only produced by seed companies.   Farmers do not save seeds for replanting because self-fertilization will result in genetic segregation of traits.  Therefore, farmers need to buy new hybrid seeds every year. This may produce an economic hardship for the farmer, who has to balance the benefits of hybrid vigour with the annual cost of purchasing new seeds.

References

Hybrid rice for food security (2004). FAO Factsheet.

Yuan L.P. (2002) The second generation of hybrid rice in China. Sustainable rice production for food security, Proceedings of the 20th Session of the International Rice Commission, Food and Agriculture Organization of the United Nations.

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