How serious are the consequences if spies steal hybrid rice seeds in my country?

Recently, the Ministry of State Security disclosed five typical cases in the field of national security. Among them, the case of "spies stealing hybrid rice parent seeds in my country" became a hot topic. Why do spy agencies steal seeds? How special are the seeds they are targeting? What impact will it have on us? Let's talk about this issue today.

Image source: CCTV News Weibo

1. What are parent rice varieties? Let’s start with hybrid vigor

I guess many people have noticed that the news report mentioned the "parent rice seeds" of hybrid rice, which are not ordinary seeds.

Before explaining what "parent rice" is, we must first understand the concept of hybridization. In biology, the mating of different species or varieties is called hybridization. For example, the hybrid rice that everyone is very familiar with is the result of the hybridization of several rice strains.

Why do we need to hybridize? This brings us to an important biological concept: heterosis. This refers to the phenomenon that the first generation of hybrids is superior to their parents in many biological properties (read this definition carefully, as you will be asked about this below).

Hybrid vigor is reflected in many organisms. In animals, hybrids have advantages in body shape, reproductive performance, meat quality, etc. For example, the mule, a hybrid of a horse and a donkey, has strong physical strength and endurance, can work under difficult conditions, and is relatively docile. In plants, hybrids are superior to their parents in growth, stress resistance, and quality. For example, hybrid rice has high yield, disease resistance, and lodging resistance. Because of this, hybridization is an important breeding strategy in agricultural production .

Schematic diagram of hybrid vigor of crops (Image source: drawn by the author)

However, hybrid breeding is not always easy. The hybrid rice that is in the Chinese people's bowl today experienced many difficulties in the past.

2. It is so difficult to obtain hybrid rice!

As early as more than 100 years ago, scientists proposed the theory that rice has hybrid vigor. However, theory is theory, and practical application is difficult. An important factor is the special nature of rice, which is monoecious. That is, there are both male and female flowers on the same plant, so rice will self-pollinate, resulting in self-fertilization, and naturally it is impossible to crossbreed and obtain hybrid vigor.

Rice flower structure (Image source: Reference 1, translated by the author)

In this case, how can people get hybrid rice?

One solution is artificial emasculation : remove the stamens of each flower and only keep the pistil, and then use the stamens of other flowers to hybridize with it (a small tip: why remove the stamens instead of the pistil? Because the stamens are mainly responsible for producing pollen, while the pistil is responsible for receiving pollen and eventually developing into fruit. If the pistil is removed, no fruit will be produced).

However, rice flowers are very small and fragmented. You can infer the difficulty of emasculating rice from the size of rice ears. Not to mention, you have to race against time with rice, otherwise it will self-pollinate (after all, this is more convenient for rice). Therefore, although the method of artificial emasculation is feasible in theory, it is very difficult to operate in practice. It is almost a fantasy to want to obtain hybrid rice on a large scale by this method.

Rice flowers (Photo source: veer Gallery)

Scientists can only seek another strategy, which is to find a rice mutant - male sterile line (abbreviated as sterile line). This kind of rice has degenerated stamens and only has pistils, which cannot be self-pollinated. It can only reproduce by hybridizing with other rice, which can greatly save human resources when developing hybrid rice.

For a long time in the past, rice breeders around the world have been struggling to find male sterile lines in nature. However, before the 1960s, this plant had never been reported, and no one knew what it looked like. The only way was to look for it in rice fields.

Image source: Reference 2

In the paper, Yuan described their search for sterile lines: the heading period of rice is generally from June to July, which is the hottest time of the year. Researchers had to use magnifying glasses and tweezers to check and select each rice plant one by one on a sunny day (and at noon, which is the hottest time). They had to identify both the flowering status of the rice and the status of the anthers. After repeated screening, they found 6 male sterile plants among more than 14,000 ears and 4 varieties.

Image source: Reference 2

Although the result was encouraging, researchers discovered in subsequent hybridization that this hybrid rice could not achieve 100% sterility in offspring. In other words, many of the offspring of these hybrids would develop into monoecious plants and gain the ability to self-pollinate (which is not good).

In order to solve this problem, scientists can only look for sterile lines in natural rice. After all, the rice in the farmland has been screened and domesticated by humans for many years, and male sterility, a trait that people don't like, is likely to be screened out. After long-term efforts, scientists finally successfully found wild male sterile plants in wild rice in Sanya, Hainan in 1970. This is the famous "wild defeat".

With wild rice, China successfully established the hybrid rice "three-line" matching system in 1973, that is, hybrid rice was achieved through three parent plants. The average yield per mu at that time increased by 20% on the basis of dwarf breeding, which means that this variety can feed an additional 70 million people each year. The success of hybrid rice is called the "Second Green Revolution" and helped China complete the transformation from "food shortage to food security."

3. Read the hybrid rice production guide and finally understand what parent rice varieties are

How did the “three-line method” produce hybrid rice? Please see the picture below.

Schematic diagram of the three-system method (Image source: drawn by the author)

The production process is roughly like this: At the beginning, we obtained a male sterile line, but the stamens of the sterile line were not developed normally, only pistils, and pollination could not be completed, so naturally it could not reproduce. Therefore, we need to find a strain that can allow the male sterile line to reproduce to be responsible for the propagation of the male sterile line. This cannot be selected casually in the rice field, but it is necessary to ensure that the male sterile line can be pollinated and the offspring are still male sterile. Therefore, this special strain is called the male sterile maintenance line (referred to as the maintenance line). With the maintenance line, we can obtain male sterile seeds in batches and realize large-scale production.

After preparing a large number of male sterile lines, the next step is to "restore" the male sterile lines so that they can regain the ability to self-pollinate. We call them male sterile restorer lines (restorer lines for short). The restorer line is another type of rice line, which is characterized by being able to transfer pollen to the pistils of the male sterile lines, achieving true hybridization and producing normal fertile seeds. When the seeds grow and bloom, they can have both pistils and stamens.

It can be seen that the realization of hybrid rice requires the cooperation of three rice parents with different functions. The sterile line is the basic requirement for hybridization, the maintainer line is used to propagate the sterile line in large quantities, and the restorer line is used to restore the sterile line to fertility and produce seeds and finally achieve hybridization. The seeds of these three parents are the "parent rice seeds" mentioned in the news.

The Chinese breakthrough in hybrid rice is not just “three-line hybridization”.

The limitations of "three-line hybridization" are mainly that the breeding process is relatively complicated, there are many operation links, and it is difficult to control the flowering period of rice plants of different strains to achieve pollination and hybridization. Therefore, people began to explore new ways to find "photothermal sterile" plants to replace the above-mentioned "genetic sterile" plants. If "male sterility" can be achieved under artificial environmental control, the complicated "three-line hybridization" can be transformed into a relatively simple "two-line hybridization" (that is, there is no need to maintain the line).

In 1973, Shi Mingsong from Shahu Seed Farm in Mianyang County, Hubei Province, discovered a rice plant called "photosensitive nuclear sterile" in the "Nongken 58" late japonica field. Through careful observation, he found that the "male sterility" and "male fertility" of this rice plant can be transformed into each other. Heading under long-day conditions will be "male sterile", while heading under short-day conditions will be "male fertile". In other words, the fertility of male stamens can be changed by regulating the length of light in the rice field . This important discovery opened the precedent for the breeding of "photosensitive nuclear sterile rice".

Based on the in-depth study of the sterility mechanism of "photosensitive nuclear sterile" rice plants discovered by Shi Mingsong, Yuan Longping proposed the development strategy of hybrid rice from "three-line method" to "two-line method" in 1987, creating a new stage of "two-line" hybrid rice breeding. In the 1990s, my country's two-line hybrid rice research made breakthrough progress, and the average per-acre yield increased by 5%-10%.

Subsequently, my country launched the "Super Hybrid Rice Breeding Research Program", which adopted the super-high-yield rice breeding theory and technical route of "combining morphological improvement with hybrid advantage utilization" to produce higher-yield hybrid rice. In recent years, with the improvement of genetic engineering, hybrid rice has begun to expand into the vast new world of the "one-line method". Combined with gene editing technology and apomixis, hybrid rice may achieve more jaw-dropping breakthroughs in the future.

Hybrid rice is now in full bloom, and many domestic rice research institutions have launched many hybrid rice varieties to meet the needs of hybrid rice cultivation under different geographical, climatic and soil conditions.

Hybrid rice has lived up to expectations, with yields rising steadily. In 2000, the yield of super hybrid rice exceeded 700 kilograms per mu, and in 2004, 2012 and 2014, it exceeded 800 kilograms, 900 kilograms and 1,000 kilograms respectively. By 2023, the yield of super hybrid rice had reached 1,251.5 kilograms per mu .

What does this mean? In the 1950s, the average yield of rice per mu was only 170 kilograms per season, and the current yield is more than 7 times that of that year . The ultra-high yield of hybrid rice has also reached more than twice the current average yield of 470 kilograms per mu per season in China. Not only that, hybrid rice has also gone abroad, and research and demonstration planting of hybrid rice have been carried out in dozens of countries around the world, with an annual planting area of ​​nearly 8 million hectares, making China's contribution to world food security .

4. Getting something for nothing! Endangering national food security!

Why is selling seeds related to national security? I believe you will understand after reading about our efforts to find hybrid rice parents.

Finding hybrid rice parents is very time-consuming and labor-intensive, and the chances are slim . We made great efforts to finally find special rice and conduct hybrid research. And in recent years, China has been investing huge manpower and material resources in hybrid rice research. The spies wanted to get something for nothing and directly obtain our hybrid rice parents. With these parents, they can directly produce hybrid rice, which directly infringes on our rights and interests.

If these germplasm resources that we have developed with great effort are spread abroad for development and utilization, they may flow back to China at high prices, causing us to bear higher seed costs and even infringements, which is also a hidden danger to our food security.

Of course, you might ask, why don't they steal ordinary hybrid rice instead of stealing hybrid rice parent seeds?

The answer is that hybrid rice, like all hybrid crops, will have separated traits and mixed good and bad varieties if its offspring is used for reproduction. Therefore, it is necessary to use parent seeds for hybridization to achieve good traits. Therefore, it is meaningless to steal ordinary hybrid rice seeds. It must be the parent rice seeds of hybrid rice .

In fact, food is the primary need of the people, and food security is one of the core of national security. Therefore, the Seed Law of the People's Republic of China issued by our country also clearly stipulates that the state has sovereignty over germplasm resources. Therefore, no unit or individual may provide germplasm resources to foreign countries without authorization!

Any unit or individual that provides germplasm resources to foreign countries, or conducts cooperative research and utilization of germplasm resources with foreign institutions or individuals, shall apply to the competent departments of agriculture, rural affairs, forestry and grassland of the State Council for approval, and at the same time submit a plan for national benefit sharing.

Because of this, we must protect germplasm resources, especially the most core parent seeds .

References:

[1] Wang, Mumei, et al. "Advances on the study of diurnal flower-opening times of rice." International Journal of Molecular Sciences 24.13 (2023): 10654.

[2] Yuan Longping. Male sterility of rice[J]. Chinese Science Bulletin, 1966, (04): 185-188.

[3] Zhu Guannan, Cao Xingsui. Breeding of hybrid rice and hybrid wheat (1960-2000) | Agricultural science and technology in New China facing the main battlefield of national economy [J]. Bulletin of the Chinese Academy of Sciences. 2019, 34(09): 1036-1045