Chinese scientists have taken a major step toward developing hybrid rice that can reproduce itself, a breakthrough that could one day make hybrid seeds much cheaper for farmers and expand their use around the world.

The research, published recently in the journal Vita, has produced a new hybrid rice variety that can generate seeds almost identical to the parent plant, allowing farmers to replant harvested seeds without losing the crop's high yield, among other desirable traits.

Compared to conventional rice, hybrid rice is known for producing higher yields and better withstands harsh growing conditions.

However, subsequent generations no longer perform like the original hybrid, requiring seed companies to produce fresh hybrid seeds every year through a complicated and labor-intensive breeding process.

As a result, hybrid rice seeds often cost several times more than conventional rice seeds, and in some cases as much as 10 times more.

The new study, led by Wang Kejian a researcher at the China National Rice Research Institute, identified a naturally occurring rice gene, HUAXU, that acts as an "on switch" for embryo development.

In field tests, more than 99 percent of the seeds produced plants that were genetic copies of the original hybrid while maintaining normal seed production and yields, Wang said.

The team began working on the "one-line method" in 2013, aiming to create a hybrid only once and allow it to reproduce itself year after year without losing its superior qualities.

In 2017, the team produced the first cloned hybrid rice seeds, but only about 5 percent of the seeds were true clones, and grain production dropped sharply.

The discovery of the HUAXU gene boosted the cloning rate to more than 99 percent while maintaining normal yields, according to the researchers.

Chong Kang, president of the Botanical Society of China and an academician of the Chinese Academy of Sciences, said the newly identified gene functions as an almost ideal "embryo activation switch", helping scientists better understand how plant embryos develop.

The technology could eventually transform hybrid rice production by allowing a successful hybrid to be developed once and then replanted for generations, reducing both seed costs and production risks, he said.

Li Jiayang, a researcher at the Chinese Academy of Sciences' Institute of Genetics and Developmental Biology, said the study has overcome a longstanding trade-off between producing genetically identical offspring and maintaining normal fertility.

The advance brings scientists closer to the goal of preserving hybrid vigor without the need to produce new hybrid seeds every year, he said.

According to Wang, the high cost of hybrid seeds has slowed their adoption. Hybrid rice now accounts for about half of China's rice-growing area, down from nearly 70 percent at its peak. Outside China, hybrid rice is grown on less than 5 percent of rice acreage despite its potential to increase production.

"If hybrid rice can reproduce itself, both seed production costs and seed prices could fall greatly," Wang said.

The technology is still in the experimental stage and is not yet ready for commercial use. The next step will be to conduct safety tests, evaluate the technology's long-term stability and further improve the system before it can be introduced into agricultural production, he said.

Web editors: Shen Jianqi, Zhang Rui