He added that while scientists have used chemicals and radiation, including gamma rays and X-rays, for decades to induce mutation in laboratories, space offers new conditions, such as microgravity, vacuums, extreme cold and a diverse range of cosmic rays.

Breeding labs can now effectively produce some of the conditions experienced in space, but replicating them all is impractical and costly, Guo said. Moreover, mutating seeds in space may produce surprising new traits more successfully than in a lab. "Space is like a super-lab for breeding new plants," he added.

Liu Luxiang, deputy director of the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, said during a public lecture last month that while space mutagenesis is a promising technology, the way in which space affects plant seeds is extremely complex and difficult to control and evaluate.

"Only a tiny fraction of seeds exposed to space will have mutations, and not all of them will produce desirable traits," he said. As a result, sending seeds into space is merely the start of creating a new variety. The bulk of the research is about growing the returned seeds in different testing fields over several generations to produce a crop that can reliably showcase desirable traits.

Scientists sometimes cross-breed space crops with other varieties to create hybrids that inherit favorable traits from their parents. Liu said. "Ground tests can be a very arduous and complicated process that typically takes at least four years to complete," he added.

Guo said his thornless peppercorn is undergoing field tests, and it is hoped that more traits can be changed to enable it to be harvested by machine, greatly increasing the yield and raising farmers' earnings. In addition to spices, crops such as peonies, wolfberries and seaberries are being improved by using space technologies.

Guo said, "Space crops have played a major role in alleviating poverty, developing local economies and creating unique products.

"Scientists' role is to enhance basic research in seed selection and breeding, and facilitate the integration of space plant breeding technologies with modern agriculture to better safeguard our nation's long-term food security."