Genome-edited rice plants whose outdoor trial cultivation has begun for the first time in Japan are pictured in Tsukuba, Ibaraki Prefecture, in this recent photo. (Mainichi)

A food research body here has started growing genome-edited rice plants outdoors on a trial basis for the first time in Japan.

The trial by the National Agriculture and Food Research Organization is a step toward practical application of genome editing, a new technology that is expected to significantly increase the yield of rice plants. However, it is not yet clear whether Japan will classify these plants as genetically modified crops, and the country has yet to formulate rules, so it remains unknown whether such crops can be introduced smoothly.

In the editing process, two genes in the rice plant are stopped from functioning through the addition of other genes that serve as "molecular scissors." By changing the plants' hormonal balance, the number of husks in each ear of rice increases, as does the size of the rice grains themselves.

The process is part of a national strategy to further develop agriculture and expand exports. The final target is a 50 percent increase in the yield of crops.

The central government approved genome editing of rice plants in April, after experts gave the green light. On May 23, the National Agriculture and Food Research Organization planted the rice in an isolated experimental paddy. The rice will be harvested in October, and officials will check whether the genome editing has had the desired effect, whether pollen is being dispersed from the plants, and whether there have been any unintended changes.

In the meantime, it remains uncertain whether crops produced through genome editing will be subject to the law restricting the release of genetically modified crops into the environment, commonly referred to as the Cartagena Act.

In the latest experiment, external genes are added to the rice plants at the cultivation stage, but as a result of repeated cross-fertilization, by the time rice becomes food, none of the added genes remain. Researchers say this is no different from natural mutation.

The question of how to deal with modified crops when none of the external genes remain has been a point of focus across the world. New Zealand, for example, restricts such crops, but Argentina does not. Full-scale discussion on the issue has not yet begun in Japan.

Resistance to genetically modified food remains strong in Japan. Consumer groups have raised concerns about the latest experiment, with one of them, Seikatsu-Club, warning that the modified crops could cross with other ones.

Hideaki Karaki, director of Japan's Foodservice Industry Research Institute, however, says there is no need for alarm.

"In cases where the added genes do not remain, it's no different from natural mutation. It's strange to focus one's worries on the process."

Akira Komatsu, a senior researcher at the National Agriculture and Food Research Organization, commented, "China is developing rice plants through genome editing at an unstoppable pace, and we're wary of international competition. We want to improve our results through trial cultivation, and strive to provide accurate information."