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Prognosis for genetic improvement of yield potential and water-limited yield of major grain crops

机译：主要粮食作物单产和限水产量遗传改良的预后

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摘要

Genetic improvement of crop yields under potential (Yp) and water scarce conditions (Yw) will be an important avenue to improved food security over the next four decades, at the end of which projected demand for food, feed and biofuel feedstock is expected to level out. Current measured relative rates of improvement in Yp and Yw for the three main cereal crops (maize, wheat and rice) in many cropping systems in the world are mostly well below the 1.l6-l.3l%y~1 rates required to meet projected demandfor cereals in 2050. These relative rates can be expected to fall further if the current absolute rates of yield improvement continue unchanged and/or the current indications of stagnation in yield improvement for some crops in some regions of the worldbecome widespread. This review assesses the available evidence for unexploited opportunities for enhancing current rates of genetic improvement for Yp and Yw, and examines some substantive proposals for achieving the same end through genetic engineeringof photosynthesis, above-ground ideotype design, and improvement of root capacity for water uptake. Because time is of the essence, special attention is paid to the time scales required to progress potentially useful traits through to proof of concept under field conditions, from there to farmer-ready cultivars, and for widespread adoption by farmers of the improved cultivars. The requirements of breeders for inclusion of potentially important traits into the conventional breeding process are outlined and the value of molecular breeding tools as aids to genetic improvement of simple and complex traits is considered. Intellectual property and regulatory requirements are taken as additional potential drags on the rates of adoption into the breeding process of useful traits and/or to the free flow of information between research teams. Main conclusions are: (a) there are some unexploited opportunities to improve Yp or Yw in some crops and/or cropping systems; (b) exploitation of these opportunities couldbe hastened by increasing funding for focussed research and by identifying and eliminating or reducing drags at various stages of the idea to farmer-ready cultivar chain; (c) the time-scales required for major improvements in yield in farmer-ready cultivars through genetic engineering or ideotype realisation are likely to be measured in decades rather than years; (d) current and expected future relative rates of progress in Yp and Yw are a matter of real concern and are insufficient to meet projected demand for cereals by 2050. Possible step changes in Yp or Yw powered by genetic improvements such as exploitation of hybrid vigour in rice or hypothetical successes in the genetic engineering of photosynthesis are unlikely to change this outlook. The pessimistic assessments embodied in the last two conclusions should not obscure the fact that without continued investment in the search for sources of genetic improvement and development of aids to breeding, the unmet demands for cereals in 2050 will be even greater.
机译：在潜在的（Yp）和缺水的情况（Yw）下，遗传改良作物产量将是未来40年改善粮食安全的重要途径，到年底，预计对粮食，饲料和生物燃料原料的需求将趋于稳定出来。目前测得的世界上许多作物系统中三种主要谷物作物（玉米，小麦和水稻）的Yp和Yw相对改善率大多远低于满足以下条件所需的1.1.6-1.3％l〜1。预计到2050年谷物需求量。如果当前的绝对增产速度继续保持不变和/或世界上某些地区某些作物的增产停滞迹象已经普遍出现，则这些相对速度可望进一步下降。这篇综述评估了尚未利用的机会来提高当前Yp和Yw遗传改良率的证据，并研究了一些通过光合作用基因工程，地上意识形态设计和提高根系吸水能力实现相同目的的实质性建议。 。由于时间至关重要，因此应特别注意在田间条件下（从那里到适合农民种植的品种）发展潜在有用特性直至概念验证所需的时间范围，并由农民广泛采用改良的品种。概述了育种者将潜在重要性状纳入常规育种过程的要求，并考虑了分子育种工具作为简单和复杂性状遗传改良的价值。知识产权和法规要求被认为是对有用性状育种过程和/或研究小组之间信息自由流通的采用率的进一步潜在拖累。主要结论是：（a）在某些作物和/或农作系统中，存在一些未利用的机会来改善Yp或Yw; （b）可以通过增加用于重点研究的资金，并通过确定和消除或减少在该构想的各个阶段对农民就绪的品种链的阻力来加快对这些机会的利用; （c）通过基因工程或表型实现大大提高农民就绪品种的产量所需的时间尺度可能是数十年而不是几年; （d）Yp和Yw的当前和预期未来相对进展速度是一个真正令人关注的问题，不足以满足2050年之前对谷物的预计需求。通过遗传改良（例如利用杂交活力）推动Yp或Yw可能的阶梯变化在水稻中或光合作用的基因工程方面的假设成功不可能改变这种前景。最后两个结论所体现的悲观评估不应掩盖这样一个事实，即如果不继续投资寻找基因改良的来源和开发育种辅助手段，2050年谷物的未满足需求将会更大。

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