Chinese scientists are close to producing a new hybrid rice that could lead to a healthier, higher-yield hybrid variety of the grain.

The two widely-grown varieties of rice in China – Japonica and Indica – have very distinct characteristics and geographical distributions. Combining the two makes the rice stronger and more resistant to pests, diseases and drought.

A team from the Crop Science Research Institute of the Chinese Academy of Agricultural Sciences (CAAS) and Nanjing Agricultural University, led by academician Wan Jianmin, believe they have conquered the challenge of rice breeding.

The scientists found that two genes work together, one as a "killer," one as a "guardian." All the hybrid offspring inherit a killer gene, which harms the pollen, causing sterility, while only some offspring inherit a guardian gene that prevents the killer from doing harm.

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CAAS professor and co-author of the paper Wu Chuanyin said: "The work amounts to revealing how the killer works."

By blocking the killer gene with genomic methods, pollen sterility can be avoided and hybrid rice created.

"In general, the further the kinship between varieties, the more significant the hybrid advantage. If a super hybrid rice can be bred between Japonica and Indica subspecies, it is predicted to yield over 15 per cent more than existing hybrid rice," said Wan.

This mechanism contributes to an effect known as a "gene drive" – a behavior that rapidly spreads a genotype within a population. During natural propagation, when rice plants carrying the killer and guardian genes are crossbred with those without them, the pollen of the hybrids without these genes becomes infertile. After several generations, the offspring carrying this pair of genes increase in number and eventually dominate.

Hybrid rice would be beneficial to human health because it would require less pesticide, added Wu, whose team have – over 30 years – identified, located and named 27 sterility-related genes, accounting for more than half of all research in this area.

China is a leading light in hybrid rice breeding, with Yuan Longping's efforts in the 1970s earning the title of "the father of hybrid rice."

Rice, the staple crop for half the world's population, is relatively costly to breed as a hybrid for a yield improvement of about 10 percent, meaning billions of people globally could be fed.

"It will be exciting to see how this mechanism can be fully exploited for biotechnology and biomedical purposes," Wan said in the paper.

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