SPACE FOOD MUTATATIONS: MASTER ESSAY

Sending seeds for short trips to space helps scientists develop new crop varieties that can thrive in the changing climate and help feed the world's growing population.

At first glance they are identical to any other ears of wheat swaying in the wind all over the world. But the vast fields of crops in north-eastern China are no ordinary plants – they were created in outer space.

They are a variety known as Luyuan 502 and are China's second most widely grown type of wheat. The plants were bred from seeds that were flown into orbit 200 miles (340km) above the Earth's surface. Here, in the unique low gravity environment and outside the protective magnetic shield of our planet, they picked up subtle changes to DNA that gave them new qualities that made them more tolerant to drought and able to better resist certain diseases.

They are an example of a growing number of new varieties of important food crops that are being bred on spacecraft and space stations while orbiting our planet. Here they are subjected to microgravity and are bombarded by cosmic rays, which trigger the plants to mutate – a process known as space mutagenesis.

While some of the mutations leave the plants unable to grow, others can be advantageous. Some become hardier and able to withstand more extreme growing conditions while others produce more food from a single plant or grow faster or require less water. When brought back to Earth, seeds from these space-bred plants undergo careful screening and further breeding to create viable versions of popular crops.

In a world facing increasing pressure on agriculture due to climate change and vulnerable supply chains, which have underlined the need for crops to be grown closer to where they are eaten, some researchers now believe that space-breeding, also known as space mutagenesis, may help them to adapt crops to these new challenges.

"Space mutagenesis makes beautiful mutations," says Liu Luxiang, China's leading space mutagenesis expert and director of the National Center of Space Mutagenesis for Crop Improvement at the Institute of Crop Sciences of the Chinese Academy of Agricultural Sciences in Beijing.

Luyuan 502, for example, has an 11% higher yield than the standard wheat variety grown in China, a better tolerance to drought and stronger resilience against the most common wheat pests, according to the International Atomic Energy Agency, which coordinates international cooperation in the use of irradiation-based techniques for creation of new crop types.

"[Luyuan 502] is a real success story," says Liu. "It has a very high yield potential and adaptability. It can be cultivated in many different areas with different conditions."

This adaptability is what makes Luyuan 502 such a hit among farmers across China's vastly diverse agricultural landscapes and varied climate.

It is just one of more than 200 space-mutated crop varieties created in China over the past 30 years, according to Liu. In addition to wheat, Chinese scientists have produced space-bred rice, corn, soybeans, alfalfa, sesame, cotton, watermelons, tomatoes, sweet peppers and other types of vegetables.

China has been experimenting with space mutagenesis since 1987 and is the only country in the world consistently using the technique. Since then it has conducted dozens of missions to carry crop seeds into orbit. Chinese scientists released the first space-bred crop – a type of sweet pepper called Yujiao 1 – in 1990. Compared to conventional sweet pepper varieties grown in China, Yujiao 1 produces much bigger fruit and is more resistant to diseases, says Liu.

China's emergence as a global space power in recent decades has enabled it to send thousands of seeds into orbit. In 2006, the country shipped into orbit their largest batch ever – more than 250kg (551lbs) worth of seeds and microorganisms of 152 species – aboard the satellite Shijian 8. In May this year, 12,000 seeds including several types of grass, oats, alfalfa and fungi, returned from a six-month visit to China's Tianhe space station as part of the crewed Shenzhou 13 mission.

The Chinese even sent a batch of rice seeds for a lunar round-trip with the Chang'e-5 mission that put a lander on the surface of the Moon in November 2020. According to Chinese news reports, these lunar rice seeds successfully produced grain in laboratory after their return to Earth.

"We benefit from China's strong space programme," Liu says. "We can use recoverable satellites, high-altitude platforms but also manned spacecraft to send our seeds to space up to twice a year and use those space utilities for crop improvement."

The seeds are sent on trips lasting from just four days to several months. In this unusual environment, a number of changes can happen to seeds and plants. First, high energy solar and cosmic radiation can damage the genetic material in the seeds itself, leading to mutations or chromosomal aberrations that are passed onto future generations. The low gravity environment could also lead to other changes. Plants that germinate and are grown in microgravity show changes in cell shape and the organisation of structures within the cells themselves.

In most cases, Chinese scientists fly the seeds into space and then germinate them back on the ground once they are returned to Earth. The seedlings are then screened for useful traits that provide an advantage over more traditional crop varieties. The scientists are looking for changes that lead to bigger fruit, lower watering requirements, better nutrient profiles, resistance to high and low temperatures or resilience against disease. In some cases rare mutations can lead to breakthroughs in crop yield or resilience.

- bbc.com