Retrospective studies are critical to investigate changes in physiological traits related to nitrogen (N) uptake and yield formation. N is a key yield-limiting nutrient in sorghum (Sorghum bicolor L. Moench), as in most crops, so improving its N internal efficiency (NIE, yield to N uptake ratio) could increase productivity and sustainability. Understanding changes in N efficiency across time linked to carbon (C) economy can provide insights for future breeding targets. This study aims to characterize N and C dynamics (via studying changes in water-soluble carbohydrates, WSC) of 20 commercial U.S. sorghum hybrids released from 1963 to 2017. Field trials were conducted during the 2018 and 2019 growing seasons in Riley County, KS. Seasonal changes in biomass accumulation, N uptake, and WSC were characterized during both vegetative and reproductive periods. Modern hybrids had greater NIE compared with those from the 1960s. Overall, beyond the yield gain documented for modern sorghum hybrids, the NIE increased at the expense of a reduction in grain N and, in minor proportion, due to increase in the N harvest index (NHI) at maturity for newer relative to older hybrids. Newer hybrids evidenced greater N remobilization from the stover to the grains during the reproductive period. This study demonstrates the physiological mechanisms for an increase in N and C utilization behind yield genetic gain for sorghum hybrids. Future yield gain in sorghum could be pursued by enhancing N uptake to sustain further genetic progress.

中文翻译：

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美国商品高粱育种回顾性研究：III．氮气内部效率

回顾性研究对于研究与氮 (N) 吸收和产量形成相关的生理特性变化至关重要。N 是高粱（Sorghum bicolorL. Moench），与大多数作物一样，因此提高其 N 内部效率（NIE，产量与 N 吸收率）可以提高生产力和可持续性。了解与碳 (C) 经济相关的氮效率随时间的变化可以为未来的育种目标提供见解。本研究旨在表征 1963 年至 2017 年发布的 20 种商业美国高粱杂交种的 N 和 C 动态（通过研究水溶性碳水化合物 WSC 的变化）。田间试验于 2018 年和 2019 年生长季节在堪萨斯州莱利县进行。生物量积累、N 吸收和 WSC 的季节性变化在营养期和生殖期都有特征。与 1960 年代的杂交种相比，现代杂交种具有更高的 NIE。总的来说，除了记录的现代高粱杂交种的产量增加外，NIE 的增加是以谷物 N 的减少为代价的，并且在较小的比例下，由于新杂交种相对于较老杂交种在成熟期的 N 收获指数 (NHI) 增加。较新的杂交种证明在繁殖期从秸秆到谷物的氮再活化更多。本研究证明了高粱杂交种产量遗传增益背后 N 和 C 利用率增加的生理机制。高粱未来的产量增加可以通过提高 N 吸收来维持进一步的遗传进展。本研究证明了高粱杂交种产量遗传增益背后 N 和 C 利用率增加的生理机制。高粱未来的产量增加可以通过提高 N 吸收来维持进一步的遗传进展。本研究证明了高粱杂交种产量遗传增益背后 N 和 C 利用率增加的生理机制。高粱未来的产量增加可以通过提高 N 吸收来维持进一步的遗传进展。