When Mr Yuan Longping passed away on 22 May 2021 at the age of 91, in Changsha, Hunan Province, China, the field of agricultural science lost a true giant. Mr Yuan was one of the greatest agricultural scientists of our time, and a hero who will be forever remembered in China and around the world. He devoted his entire life to the research of hybrid rice and made great contributions to global food security and poverty alleviation.

袁隆平于2021年5月22日在中国湖南省长沙市去世，农业科学领域陨失了一位真正的伟人。袁先生是我们这个时代最伟大的农业科学家之一，是在中国和全球永远被铭记在心的英雄。他毕生致力于杂交水稻的研究，为全球粮食安全和扶贫工作做出了巨大贡献。

Yuan Longping was born in Beijing in 1930 and received his agronomic degree from Southwest Agricultural College (now Southwest University) in 1953. Subsequently, he began his teaching career at Anjiang Agricultural School in Hunan Province, China. In the face of severe famine at that time, he was determined to use agricultural science and technology to defeat the threat of hunger. As rice was a staple crop and had great potential for yield improvement, he began to study rice breeding to solve the problem of food shortages in China and many developing countries.

袁隆平1930年生于北京，1953年于西南农学院（现西南大学）获得农学学位。随后，在中国湖南省安江农校任教。面对当时严重的饥荒，他决心用农业科技战胜饥饿的威胁。由于水稻是主食作物，具有很大的增产潜力，他开始研究水稻育种，以解决中国和许多发展中国家的粮食短缺问题。

Credit: Lu Boan / Xinhua / Alamy Live News

In 1961, Yuan Longping unexpectedly found an ‘outstanding’ rice plant with excellent characteristics (large panicles and full grains). He carefully collected the seeds of this plant and planted more than 1,000 seeds the following year. Surprisingly, the traits of the offspring were segregated, and the elite phenotype was lost. Yuan was curious about the reason underlying the huge difference between the offspring and the parents. After careful analysis, he suggested that this ‘outstanding’ rice was a natural hybrid rice — therefore proposing that rice could be hybridized — which cast doubts on the popular authoritative theory that self-pollinated plants, such as rice, had no heterosis and were not suitable for hybridization. This interesting finding fuelled his enthusiasm in the study of hybrid rice, and thus determined his main research direction. Mr Yuan first proposed ‘the three-line matching method’ in the paper ‘Male sterility in rice’ published in 1966, laying the scientific foundation for breeding hybrid rice. ‘Three-line’ refers to three lines of hybrid rice: male-sterile line, male-sterile maintainer line and male-sterile restorer line.

1961年，袁隆平意外地发现了一株“凸出”的水稻，具有穗大、粒满的优良特性。他小心地收集了这棵水稻的种子，第二年种下了1000多粒种子。令人惊讶的是，后代的性状出现分离，优良表型丢失。袁先生对子代和亲本之间巨大差异的原因很好奇。经过仔细分析，他认为这棵“凸出”的水稻是一种天然杂交水稻——因此提出水稻可以杂交——这挑战了当时流行的权威理论，即当时普遍认为水稻等自花授粉植物没有杂种优势，也不适合杂交。这一有趣的发现激发了他对杂交水稻研究的热情，从而决定了他的主要研究方向。袁先生在1966发表的《水稻的雄性不孕性》一书中首次提出了“三系交配法”，为杂交水稻育种奠定了科学基础。“三系”是指杂交水稻的三个品系：雄性不育系、雄性不育保持系和雄性不育恢复系。

Because rice is a self-pollinating plant, it is extremely difficult to remove stamens manually for the production of hybrid seeds in large quantities. Moreover, heterosis is only obvious in the first generation of hybrids, which must be prepared for every planting cycle. This becomes the bottleneck in developing hybrid rice for agriculture, with the key solution being to breed with a male-sterile parent. Mr Yuan’s discovery of natural hybrid rice inspired him to search for natural male-sterile rice with stamens that did not develop normally and pistils that could accept foreign pollen to reproduce hybridized offspring. The male-sterile plant, if it were to be found, would ideally be the female parent, which could then be crossed with other varieties to breed hybrid rice. With this in mind, Mr Yuan began to look for natural male-sterile rice plants. The search started in cultivated rice, where six male-sterile plants were found, but their male-sterile traits could not be maintained in the offspring. Mr Yuan and his team then expanded their search to wild rice and tried to perform distant hybridization. In 1970, they finally discovered a male-sterile wild rice plant called ‘wild abortive’ (WA). In 1973, the team harvested WA offspring which comprised tens of thousands of male-sterile rice plants — a milestone in the development of hybrid rice. WA has contributed ~95% of the male sterility source in the entire collection of hybrid rice developed worldwide so far. Although the process of discovering WA was long and challenging, Mr Yuan and his team remained confident. This confidence emerged from the clear research direction and their expertise on male-sterile phenotyping. Chance favours the prepared mind, and when encountering WA, they recognized the treasure at a glance.

由于水稻是一种自花授粉植物，通过人工去除雄蕊获得杂交种子极为困难。此外，杂种优势只在第一代杂种中明显，因此必须为每个种植周期做好杂交种子供应。这成为了农业上发展杂交水稻的瓶颈，解决该问题的关键是利用雄性不育亲本进行育种。袁先生对天然杂交水稻的发现启发他去寻找雄蕊发育不正常、雌蕊能接受外来花粉，从而繁殖杂交子代的天然雄性不育水稻。如果能找到雄性不育株，将会成为理想的母本，然后可以用来与其他品种的水稻进行杂交，培育杂交水稻。考虑到这一点，袁先生开始寻找天然雄性不育水稻。袁先生首先从栽培稻中开始寻找，共发现了6株雄性不育植株，但其雄性不育性状在子代中无法保持。袁先生和他的团队随后将搜索范围扩大到野生稻，并尝试进行远缘杂交。1970年，他们终于发现了一种名为“野败”的雄性不育野生稻。1973年，袁先生的团队收获了由数万株雄性不育水稻组成的“野败”子代，这是杂交水稻发展的一个里程碑。迄今为止，全世界杂交水稻中约95%的雄性不育来自于“野败”。尽管发现“野败”的过程漫长且富有挑战性，但袁先生和他的团队仍然充满信心。这种信心来自于明确的研究方向和他们在雄性不育表型鉴定方面的专长。机会偏爱有准备的人，当他们遇到“野败”时，他们一眼就认出了宝藏。

After establishing the sterile line and the maintainer line, the next step was to find a suitable restorer line, the last tie of the three-line matching to realize the utilization of heterosis. In 1973, Mr Yuan joined the Hybrid Rice Research Collaborative Group of the Hunan Academy of Agricultural Sciences and accelerated the progress of developing the three-line matching method. He found a suitable restorer line that closed the loop and led to breeding of the hybrid rice ‘Nanyou 2’. By successfully developing the first hybrid rice varieties, Mr Yuan made tremendous contributions to the Green Revolution in agriculture, and he is recognized as the ‘father of hybrid rice’ in China.

在建立了不育系和保持系后，下一步就是寻找合适的恢复系，最后对三系进行交配，实现杂种优势的利用。1973年，袁先生加入湖南省农科院杂交水稻研究协作组，加快了三系交配法的开发进度。袁先生找到了一个合适的恢复系，组成了三系，并成功选育出了杂交水稻“南优2号”。袁先生成功创制出了第一批杂交水稻品种，为农业绿色革命作出了巨大贡献，在中国被誉为“杂交水稻之父”。

The advent of high-yield hybrid rice greatly alleviated China’s food problems, increasing the yield of conventional rice by about 20%. After making significant progress in the 1970s, Mr Yuan generously shared the results of the three-line method with domestic and international agronomists for no profit. In 1980, he volunteered to donate key rice varieties to the international community, and later trained farmers in Africa, Southeast Asia and South Asia to grow hybrid rice. The hybrid rice technology has been introduced and promoted in more than 40 countries around the world, and the cultivated area outside China has reached 9 million hectares.

高产杂交水稻的出现大大缓解了中国的粮食问题，使水稻增产20%左右。在上世纪70年代取得重大进展后，袁先生将三系法的成果慷慨地与国内外农学家进行分享，并且不收取任何费用。1980年，他主动向国际社会捐赠了核心水稻品种，后来在非洲、东南亚和南亚培训农民种植杂交水稻。目前，杂交水稻技术已在全球40多个国家被引进和推广，中国境外种植面积已达900万公顷。

After developing the three-line breeding method, Mr Yuan continued to seek breakthroughs to simplify the process of seed production. In the 1980s, Mr Yuan proposed to improve the hybrid rice breeding strategy from the three-line hybrid rice strain to a two-line variety, and finally to a one-line variety. The two-line method uses temperature-sensitive or photosensitive sterile materials as the sterile line, omitting the propagation process of the maintainer line, whilst the one-line method refers to a breeding technique that uses apomixis to fix the heterosis, and does not require annual seed production. This method could greatly reduce the cost of seed production and could maximize the application of heterosis. While the two-line method has been successfully developed and applied, the one-line method is not yet available. Mr Yuan’s work had to stop here, but the search for the one-line method continues.

在开发出三系育种法之后，袁先生继续寻求突破，以简化种子生产过程。上世纪80年代，袁先生提出将杂交水稻育种策略从三系杂交稻品种改为两系杂交稻品种，最后实现一系杂交稻品种。两系法采用温敏或光敏不育材料作为不育系，省去了保持系的繁殖过程，而一系法是指利用无融合生殖来固定杂种优势的育种技术，不需要每年生产种子。这种方法可以大大降低制种成本，最大限度地利用杂种优势。虽然两系法已被成功开发和应用，但一系法尚不可用。袁先生的工作不得不到此为止，但对一系法的探索仍在继续。

Mr Yuan Longping was credited with a long list of awards and prizes, including China’s first special invention award in 1981, the UNESCO Prize for Science in 1987, the Nikkei Asia Award in 1996, the State Preeminent Science and Technology Award in 2000, the Wolf Prize in Agriculture and the Word Food Prize in 2004. He was elected as a member of the Chinese Academy of Engineering in 1995, and as the foreign associate of the United States National Academy of Sciences in 2006. Mr Yuan has won numerous titles and awards throughout his life, but these were not his pursuits. In a 2019 interview with China Central Television, he said that he had two dreams: one was “for super rice to grow taller than sorghum, with stems each ear as long as a broom, and each grain as big as a peanut”, so he could “enjoy the cool underneath the rice crops”; the other was for “hybrid rice [to] be grown all over the world.” For decades, Mr Yuan and countless researchers worked hard to realize these dreams. It is sad that Mr Yuan has left us, but his dreams are carried by many plant and agricultural researchers.

袁隆平先生获奖无数，包括中国第一个特等发明奖（1981年）、联合国教科文组织科学奖（1987年）、日经亚洲奖（1996年）、国家最高科学技术奖（2000年），沃尔夫农业奖和世界粮食奖（2004年）。袁先生1995年当选为中国工程院院士，2006年当选为美国国家科学院外籍院士。袁先生一生中获得过无数的头衔和奖项，但这些并不是他的追求。在2019年接受中央电视台采访时，他说他有两个梦想：一个是“超级稻长得比高粱还高，穗子有扫帚那么长，接的子有花生那么大，叫做禾下乘凉梦”；另一个是“杂交水稻覆盖全球梦”。几十年来，袁先生和无数的研究人员努力工作，致力于实现这两个梦想。袁先生永远地离开了我们，这很让人难过，但是他的梦想却被许多植物和农业研究人员所承载。

Mr Yuan Longping generated high-yield hybrid rice by proposing plant genetic theories and achieving practical field production. His breakthrough boosted the development and application of high-yield hybrid rice, and important contributions were also made by many other talented rice researchers. Mr Yuan’s legacy is not only the progress of hybrid rice — his curiosity, devotion, courage, perseverance, diligence, cooperation and selflessness have left an indelible spiritual wealth to us all.

袁隆平先生通过提出植物遗传理论，实现实际大田丰产，培育出了高产杂交水稻。他的突破推动了杂交水稻的高产开发和应用，其他许多有才华的水稻研究人员也做出了重要贡献。袁先生给我们留下的不仅仅是杂交水稻的进步——他的好奇心、奉献精神、勇气、毅力、勤奋、合作和无私同样给我们大家留下了不可磨灭的精神财富。

作者：王克剑