Nature Plants: 中国水稻所王克剑研究员发文悼念袁隆平院士(1930-2021)

2021年5月22日，91岁的袁隆平先生在中国湖南长沙逝世，农业科学领域失去了一位真正的巨人。袁先生是我们这个时代最伟大的农业科学家之一，也是一位将永远被中国和全世界铭记的英雄。他毕生致力于杂交水稻的研究，为全球粮食安全和减贫事业做出了巨大贡献。

袁隆平1930年生于北京，1953年获西南农学院(现西南大学)农学学位。随后，他开始了他的教学生涯在中国湖南省安江农业学校。面对当时严重的饥荒，他决心利用农业科学技术战胜饥饿的威胁。由于水稻是主要作物，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。

1961年，袁隆平意外地发现了一株“优秀”的水稻植株，它具有优良的特性(大穗全粒)。他小心翼翼地收集了这种植物的种子，并在第二年种下了1000多颗种子。令人惊讶的是，后代的性状被分离，精英表型被丢失。袁很好奇这个孩子和父母之间巨大差异背后的原因。经过仔细分析，他认为这个“优秀”的水稻是一个自然杂交稻，因此提出了水稻可以杂交的观点，这对当前流行的权威理论——自花授粉植物，如水稻，没有杂种优势，不适合杂交——提出了质疑。这一有趣的发现激发了他对杂交水稻的研究热情，从而确定了他的主要研究方向。袁先生在1966年发表的《水稻雄性不育》一文中首次提出了“三系配套法”，为杂交水稻的选育奠定了科学基础。'三系’是指杂交水稻的三系: 不育系、保持系和不育恢复系。

由于水稻是自花授粉植物，在大批量生产杂交水稻种子时，手工去雄是极其困难的。此外，杂种优势只有在第一代杂种中表现明显，必须为每一个种植周期做好准备。这成为发展农用杂交水稻的瓶颈，关键的解决办法是与不育的父本进行杂交。袁先生发现的自然杂交水稻激发了他寻找自然雄性不育水稻的灵感，这些水稻的雄蕊不能正常发育，雌蕊可以接受外来花粉繁殖杂交后代。如果能找到不育株，最好是母本，然后与其他品种杂交培育杂交水稻。考虑到这一点，袁先生开始寻找自然雄性不育水稻植株。研究从栽培水稻开始，在栽培水稻中发现了六株雄性不育植株，但其雄性不育性不能在后代中保持下去。袁先生和他的团队随后将搜索范围扩大到野生稻，并试图进行远缘杂交。1970年，他们终于发现了一种雄性不育的野生稻，称为“野败”(WA)。1973年，研究小组收获了几万株雄性不育水稻后代，这是杂交水稻发展史上的一个里程碑。到目前为止，杂交水稻的雄性不育来源中，WA 贡献了95% 。虽然发现 WA 的过程漫长而充满挑战，但袁先生和他的团队仍然充满信心。这种信心来自于清晰的研究方向和他们在雄性不育表型方面的专业知识。机会偏爱有准备的人，当遇到西澳时，他们一眼就认出了宝藏。

在建立不育系和保持系之后，下一步就是找到一个合适的恢复系，即三系配套的最后一条，以实现杂种优势的利用。1973年，袁先生加入湖南省农业科学院杂交水稻研究协作组，加快了三系配套技术的发展进程。他找到了一个合适的恢复系，封闭了杂交水稻“南优2号”的恢复系。袁先生成功开发了第一批杂交水稻品种，为农业绿色革命做出了巨大贡献，被誉为中国“杂交水稻之父”。

高产杂交水稻的出现极大地缓解了中国的粮食问题，使常规水稻的产量增加了约20% 。在70年代取得重大进展之后，袁先生慷慨地与国内外农学家分享了三线法的成果，而且没有任何利润。1980年，他志愿向国际社会捐赠关键的水稻品种，后来又培训了非洲、东南亚和南亚的农民种植杂交水稻。杂交水稻技术已在世界40多个国家引进和推广，中国以外的种植面积已达到900万公顷。

在发展了三系育种方法后，袁先生继续寻求突破，以简化种子生产过程。20世纪80年代，袁先生提出将三系杂交水稻改良为两系杂交水稻，最终形成单系杂交水稻。两系法是以温敏或光敏不育材料为不育系，省略了保持系的繁殖过程，而一系法是利用无融合生殖固定杂种优势，不需要每年生产种子的育种技术。这种方法可以大大降低种子生产成本，最大限度地发挥杂种优势。虽然两线法已经得到了成功的发展和应用，但是一线法还不可行。袁先生的工作到此为止，但对单行方法的研究仍在继续。

袁隆平先生获得了很多奖项，包括1981年中国的第一个特殊发明奖，1987年的联合国教科文组织科学奖，1996年的日经亚洲奖，2000年的中华人民共和国国家最高科学技术奖，2004年的沃尔夫农业奖和世界粮食奖。1995年当选为中国工程院院士，2006年当选为美国国家科学院院士。袁先生一生中赢得了无数的头衔和奖项，但这些并不是他的追求。在2019年接受中国中央电视台采访时，他表示自己有两个梦想: 一个是“让超级水稻长得比高粱还高，每个穗子长得像扫帚一样长，每粒谷子长得像花生一样大”，这样他就可以“享受水稻作物下面的凉爽”; 另一个梦想是“让杂交水稻在世界各地生长”几十年来，袁先生和无数的研究人员为实现这些梦想而努力工作。袁先生离开了我们，这很悲哀，但是他的梦想被许多植物和农业研究人员所承载。

袁隆平先生通过提出植物遗传学理论，实现大田生产，培育出高产杂交水稻。他的突破促进了高产杂交水稻的开发和应用，其他许多优秀的水稻研究人员也做出了重要贡献。袁先生的遗产不仅仅是杂交水稻的进步ーー他的好奇心、奉献精神、勇气、毅力、勤奋、合作和无私为我们所有人留下了不可磨灭的精神财富。

作者介绍：

王克剑（中国水稻研究所研究员）

王克剑，男，1983年12月出生，籍贯江苏盐城。  博士。中国水稻研究所研究员。  主要研究方向为：遗传重组机制及应用研究；植物繁殖习性研究；水稻重要农艺性状基因克隆及功能研究。

2020年8月，获得2020年度陈嘉庚青年科学奖之生命科学奖

王克剑研究员现任水稻生物学国家重点实验室副主任、中国农业科学院科技创新工程基因组编辑及无融合生殖创新团队首席科学家；中国作物学会理事、中国遗传学会基因组编辑分会委员；担任BMC Plant Biology、Frontiers in GenomeEditing副主编, aBIOTECH、《作物学报》等期刊编委。

2004年7月获扬州大学农学学士学位；2009年7月获中国科学院遗传与发育生物学研究所理学博士学位，同时留所工作任助理研究员；

2012年1月起任副研究员。2013年8月加盟中国水稻研究所任所特聘研究员2020年8月，获得2020年度陈嘉庚青年科学奖之生命科学奖（获奖项目：利用基因组编辑技术建立杂交水稻无融合生殖体系）。

PS: 全文

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.

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.

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 rice1. 'Three-line’ refers to three lines of hybrid rice: male-sterile line, male-sterile maintainer line and male-sterile restorer line.

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.

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.

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.

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 variety2. 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.

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.

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.

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