How a good rice variety is cultivated

In April 2022, General Secretary Xi Jinping visited Hainan and came to the "brain" of the National South China Seed Research and Breeding Base - the Yazhou Bay Seed Laboratory in Sanya City. The General Secretary said: "Only by holding Chinese seeds with our own hands can we hold China's rice bowl firmly and achieve food security."

The "Southern Breeding" is a journey of repeated migration for a large number of agricultural workers. From September to May of the following year, they come to Hainan from all over the country to carry out a series of scientific research activities such as crop seed breeding using the unique tropical climate conditions here. The name "Southern Breeding" comes from this.

Now is the time for rice seed breeding in the south. Let us follow a rice seed and observe its growth process from material creation to breeding and seed production.

Sampling - Sanya, Hainan

It takes 10 years of hard work to produce a good variety

Some are just seedlings after being sown, some are green and heading, and some are already golden and ready to be harvested - walk into the Sanya South Breeding Base of China Seed Group, and you can see rice in various growth stages.

"Hainan's advantage is that it has abundant light and temperature resources. We have to sow seeds once every one or two months here." Shi Yitao, a rice breeding assistant at China Seed Group, is a good hand at farming. "We know everything that farmers can do, and we also understand what farmers cannot do."

For a year, he watched over the experimental field like taking care of a child, and his broad face was tanned. "Every day, I watered the field diligently and observed carefully, protecting it from snails, birds and mice. I just wanted every seedling to sprout and grow healthily," said Shi Yitao.

Strong wind, heavy rain and strong sun, this is how people in southern China summarize the local climate.

When sowing under the scorching sun, sometimes, he had to hide from rain four or five times in half a day. Whenever it rained, Shi Yitao was always worried: when the seedlings were small, he was afraid that a heavy rain would wash away the nutrient soil and the seedlings; when the rice was a little bigger, a typhoon would hit, and the water in the field would accumulate to more than 60 centimeters, leaving only the ear head on the water surface. He waded through the water again and again in the wind and rain to drain the water. "I'm not afraid of danger, nothing is more important than saving the seedlings."

In a corner of the experimental field, the iron fence is deeply embedded in the soil, and a small piece of rice field has received special care. "It is specially used to prevent rats from chewing the materials." Shi Yitao gently opened the iron door, walked across a ridge, and the green and tall rice seedlings came into view.

"These are the breeding materials R1607 that have been introduced with low-cadmium genes. They are already in the tillering stage." Shi Yitao said as he bent down and used tweezers to take off leaves about 1 cm long and carefully placed them in the deep-well plate. "I hope the sampling will be successful in one go."

From the summer of 2021 to now, this batch of materials has been planted in Hainan for three consecutive seasons, plus one season in Hainan in the winter of 2020 and one season in Hubei in early 2021. Over two years, hybridization, backcrossing, and self-pollination have been continuously carried out for five generations. The initial laboratory test data showed that the genetic traits of the low-cadmium gene have already appeared in the offspring.

"If the re-inspection data is correct, we can select the one with the best growth and the best laboratory genetic data from these 2,000 plants for trial planting after they mature," said Shi Yitao.

Would it be too little to just pick one?

"Don't underestimate it. It has a high fruit set rate, with one plant producing 1,000 to 2,000 grains, and the rice ears are half the length of an arm. This is why the rice variety Tsuen Yu 607 is favored by the market."

"If you compare Tsuen U 607 to an excellent 'baby', then R1607 is like an excellent 'father'." Zhou Hua, director of rice testing at China Seed Group, said that R1607 not only aggregates 8 rice blast resistance genes and 3 lodging resistance genes, but also aggregates sheath blight resistance, cold tolerance, flood tolerance, nitrogen high efficiency genes and 17 yield genes. Now that the low-cadmium gene has been introduced, rice will have low adsorption or insensitivity to cadmium even if it is planted in fields with excessive cadmium content.

How long does it take to cultivate a high-quality variety like Tsuen U 607?

"It took a full 10 years from breeding to variety approval!" Zheng Ruifeng, head of the R&D team of Tsuen U 607 and director of rice breeding at China Seed Group, said that creating new materials is highly uncertain. "We made 52 hybrid combinations, but only R1607 was finally bred."

The R&D team will then introduce genes for resistance to bacterial blight, resistance to rice planthoppers, and fragrance genes, and continue to upgrade and transform R1607 to become an all-around champion, so that the "babies" born in this way will be even better. What is the most difficult part of breeding?

Zheng Ruifeng replied: If a variety with excellent performance is planted in other places for trial, some unexpected situations may occur, such as not being resistant to high temperatures or low temperatures, sometimes not being resistant to lodging, not being resistant to a certain disease, or being sensitive to a certain climate. "This will make all previous efforts and investments go to zero."

Early research and development is difficult, but we are not too worried. Once we enter large-scale production, we will be very nervous. The larger the promotion area, the more worried we will be. "If the farmers have a poor harvest, we will be worried. We will feel relieved when the harvest comes," said Zheng Ruifeng.

Testing - Wuhan, Hubei

Breeding experts put on "gene glasses"

In Wuhan City, Hubei Province, the genetic typing laboratory of the Life Science and Technology Center of China Seed Group, the low-cadmium samples sent from the Sanya base finally ushered in the key experimental link - extracting DNA genetic material and conducting genetic analysis.

Zhang Xiaobo, the head of the laboratory, tapped the button, and the shaker, centrifuge, and PCR instrument started running one after another. The data showed that the response rate of differential sites was 88.7%, and the response rate at the whole genome level reached 97.5%.

What do these data mean? "This shows that the low-cadmium gene has indeed been stably inherited by the offspring of R1607. After the upgraded version of R1607 matures, a new trial production process can be started," Zhang Xiaobo explained.

"During the breeding process, the laboratory and the experimental field are closely linked." Ye Rongjian, deputy director of the Technology Platform Department of the Science and Technology Center of China Seed Group, said that the genetic performance after the introduction of the low-cadmium gene is difficult to observe based on experience. "Whether the cadmium element is absorbed into the rice grains cannot be seen with the naked eye."

"When we first created R1607, molecular biological breeding technology was just beginning, and we took the path of traditional hybrid breeding combined with molecular breeding-assisted selection. Now molecular marker testing and genomic breeding technology are very common. It is like giving breeding experts a pair of glasses that can see through gene functions." Zheng Ruifeng said that future smart breeding, relying on artificial intelligence, big data and biotechnology, will be more efficient and accurate.

Of course, the powerful function of this pair of "glasses" depends on the breakthrough of basic research. "The reason why the introduction of low-cadmium genes has produced results in more than two years is that the functional sequence of low-cadmium genes is very clear." Ye Rongjian introduced that rice is expected to have about 50,000 genes, and about 4,000 genes have been cloned and their functions have been clarified. It may take many years to understand the function of a gene, and there is still a long way to go in the future.

"The laboratory not only undertakes testing and analysis tasks, but also explores the mysteries of genes." Seed manager Nie Dongming pushed open the heavy security door, and the germplasm resource bank that stores more than 100,000 rice materials appeared in front of him. Here, at a temperature of 4 degrees Celsius, the seeds enter a dormant state and can be safely stored for 5-10 years.

Zhou Hua said that the germplasm resource bank is a treasure trove for creating breeding materials. Academician Yuan Longping discovered the special material of wild rice sterile plant "Yebai" in Sanya, which led to a breakthrough in hybrid rice breeding.

The breakthrough in R1607's resistance to rice blast was also due to the germplasm resource bank. "At that time, we were making a breakthrough in the technology of resisting rice blast, and we heard that the Chinese Academy of Sciences had discovered a gene that was very resistant, but the breeding experts did not have this material. So we went to the germplasm resource bank to search, and surprisingly found the original material." Zheng Ruifeng introduced that this farmer's variety was hybridized and backcrossed with indica rice varieties to breed a series of materials containing the gene for resistance to rice blast.

"If something in nature is lost, you may not be able to find it when you want to use it in the future. People are now increasingly aware of the importance of germplasm resource banks." Zheng Ruifeng said that when its value is not clear and the advantages of germplasm resources have not been tapped, it is a kind of protection at the source.

Zhou Hua introduced that China Seed Group and Yazhou Bay Seed Laboratory jointly issued a list to the first-class scientific research institutes and universities in China, integrating gene resources through industry-university-research cooperation, with more than 10 projects in the field of rice alone. In addition to further cooperative research on low-cadmium genes, there is also cooperation in herbicide resistance and rice false smut resistance. "The goal is to make excellent rice varieties full of treasures."

Seed production——Hainan Oriental

One mu of seed production can supply more than 100 mu of fields

"Yanmei, throw me some seedlings!" "Okay, take them!" Fu Yanmei didn't even raise her head, and a bunch of tender green rice seedlings flew out of her hand, flew over eight or nine women who were working hard, drew an arc above the paddy field, and was accurately "delivered" to Zeng Yabei's side.

On February 3, Gancheng Town, Dongfang City, Hainan Province, has been busy with rice seed production and transplanting for more than a week after the Spring Festival. The villagers cooperated skillfully, and they chased each other in the fields, and bursts of laughter could be heard from time to time.

Such busy and cheerful scenes often appear in the seed production process. The most attractive part of the whole seed production process is heading and flowering, also known as pollination.

The sky cleared up, the temperature rose, and the male and female materials in the rice fields blossomed. The pale yellow flowers dotted the light green rice ears and swayed gently in the breeze. A 40-meter-long rope was hung on the rice ears in an arc. Two workers, each holding one end, walked forward in parallel. Wherever the rope passed, the rice ears touched, the stamens trembled, and the pollen floated to the female pistil. In an instant, light yellow powder mist swirled in the field.

Wang Shiming, general manager of Hainan Nong Le Nanfan Technology Company, said: "Breeding means bringing a bag of seeds and carrying a bag of seeds back. Seed production is different. One mu of seed production can supply more than 100 mu of fields."

There are many seed production processes, and the sowing schedule must be reversed to allow the parent plants to bloom at the same time. For example, it takes 100 days from sowing to flowering for the male plant of Tsuen U 607, and 80 days for the female plant, so the male plant must be sown 20 days in advance; then the leaf stage is constantly observed, the flowering period is analyzed, and sometimes water and fertilizer are adjusted to ensure that the flowering periods coincide.

"Artificial powdering can improve the fruiting rate of hybrid rice." Wang Shiming introduced that many years ago, there were as many as 100,000 "seed production troops" from Pingxiang City, Jiangxi Province in Hainan. In recent years, the country has revitalized the seed industry, and Pingxiang has also introduced measures such as subsidies for large seed producers and subsidies for grain production. Encouraged by this, many Jiangxi farmers who were producing seeds in Hainan have returned to their hometowns to develop.

"I have been able to do everything from raising seedlings and transplanting, heading and pollinating, harvesting and drying seeds, to selecting and packaging seeds since I was a child." Wang Shiming has been following his father to Hainan to produce seeds for more than 20 years. His skin is tanned and he speaks slowly. Dongfang City, where he lives, was recognized as a national seed-producing county in 2022. The land of one million mu of Gratitude Plain is fertile. "Winter seed production starts at the end of December every year, and the seeds are harvested in April and May of the following year, which happens to be the time for seedlings to be planted in the middle and lower reaches of the Yangtze River."

Affected by the rising land rent and labor costs, Hainan's rice seed production has been moving westward, from Sanya City to Ledong Li Autonomous County, and then to Dongfang City. "The average annual transfer price of land in Dongfang is 1,300 yuan per mu, while in Sanya it has already exceeded 3,500 yuan," said Wang Shiming.

In mid-to-late September 2022, when Wen Mincao, deputy manager of the production department of Zhongzhong Agricultural Technology Company, received an urgent task to increase the seed production area of ​​Quanyou 607 in Hainan from the original 6,000 to 7,000 acres to more than 20,000 acres, his head was buzzing. Where could he find manufacturers and production bases?

Zhongzhong implements an order system, and every year it issues plans to producers and professional teams across the country. However, the winter farming season in the mainland has passed, making it difficult to produce seeds; although Hainan can produce seeds, it is the winter vegetable season, with little vacant land, high land rent, and early seed delivery time, so the "grabbing of bases" was a bit fierce.

Thanks to Wang Shiming's contacts, Wen Mincao reached an agreement on 6,000 mu of land in just one week, and finally breathed a sigh of relief. "The major seed-producing counties support the integration of production, processing, warehousing, packaging and logistics. Under favorable policies, we signed a production and supply chain integration cooperation framework with local manufacturers, producing and packaging on site and sending them to the market. The unsold seeds can be stored on site."

Every effort is worth it.

In the middle and lower reaches of the Yangtze River, farmers who have tasted the sweetness have long been thinking about good seeds. In Shilou Village, Wudian Town, Zaoyang City, Hubei Province, grain grower Chen Bangguo calls Wudian Town seed dealer Qiu Yunze every two or three days after planting winter wheat.

"Good seeds are in great demand! When I was trying to plant Tsuen Yu 607, it was Lao Qiu who came to me to sell it. He guaranteed that he would compensate me for the yield if the seeds were not good. As a result, I harvested 200 to 300 kilograms more rice per mu of land. I happily invited Lao Qiu to dinner!" Chen Bangguo said. "In the early stage, we built a model field for display, and invited large farmers to observe the harvest and yield measurement on site, so that more farmers can see the comparative advantages of varieties. In the later stage, we collected information on high-yield farmers, made promotional posters, and organized seedling viewing meetings from the seedling stage to the heading stage to expand the influence." Speaking of the promotion experience of good seeds, Wang Hanyong, deputy sales manager of Hubei District of China Seed Group, talked endlessly.

In the field of hope, season after season, the story of a good seed will continue to be told.