Exploring the density tolerance yield potential paradigm

玉米（Zea mays L.）育种家在商品谷物产量的持续遗传改良方面取得了极大的成功。在美国，在65-70年的时间里，这一进展约为每年2%，即每年117公斤/公顷，加拿大在杂交时代也观察到类似的进展（每年80公斤/公顷）。过去65-70年的遗传改良是玉米植株生理特性变化的结果。但并不是所有的生理方面都发生了变化。在谷物产量增加近7倍的同时，一般的非生物胁迫耐受性也得到了同样令人印象深刻的增强：在此期间，植物种群密度胁迫、氮胁迫、低温胁迫、水分胁迫、杂草竞争和除草剂耐受性都得到了增强。令人惊讶的是，考虑到选择的“积极”意外后果，产量潜力并没有改变。为什么通过集约化育种，植物种群密度显示出遗传改善，而产量潜力却保持不变？本文探讨了植物种群密度耐受性与产量潜力之间的关系。毫无疑问，未来玉米产量的提高将通过育种方法和理念的不断发展而实现。通过拟议的研究获得的好处是获得新的知识和专业知识，这可能导致加拿大玉米育种行业未来使用的玉米育种选择方法的范式转变。

Maize (Zea mays L.) breeders have been extremely successful in making continuous genetic improvement in commercial grain yield. In the US, over a 65-70 year period this progress amounts to approximately 2% per year or 117 kg/ha per year, with similar gains observed in Canada during the hybrid era (80 kg/ha per year). The genetic improvement over the past 65-70 years is the result of changing physiological attributes of the corn plant. But not all physiological aspects have changed. Accompanying this nearly 7-fold increase in grain yield was an equally impressive enhancement in general abiotic stress tolerance: plant population density stress, nitrogen stress, cold temperature stress, water stress, weed competition, and herbicide tolerances have been enhanced during this period. Surprisingly, in light of the 'positive' unintended consequences of selection, is that yield potential did not change. Why has plant population density shown genetic improvement through intensive breeding efforts, while yield potential has remained unchanged? This proposal explores the relationship between plant population density tolerance and yield potential. Future gains in maize grain yields will no doubt come about through continued evolution of breeding methodologies and philosophies. Benefits derived via the proposed research are acquisition of new knowledge and expertise that may result in a paradigm shift with regards to future maize breeding selection methodologies utilized by the Canadian maize breeding industry.