Understanding physiological changes in response to long-term selection for yield can inform breeding decisions and hasten genetic gain. The objective of this study was to characterize changes over time in yield-relevant physiological traits for hybrids with different years of release for grain sorghum (Sorghum bicolor L. Moench). Field trials were conducted during the 2018 and 2019 seasons in 8 site-years across the states of Kansas and Texas including 20 commercially available grain sorghum hybrids released by Pioneer between 1963 and 2017. Detailed yield-related physiological traits were determined in 2 site-years including grain yield and its components, grain filling, plant biomass, panicle length, and water-soluble carbohydrates (WSC) during the reproductive period. Consistent with estimates using historical yield data, sorghum yield improvement was 27 kg ha⁻¹ yr⁻¹. For the 2 site-years with detailed yield-related physiological traits, no changes in final grain weight, grain-filling duration, and rate over time were documented. In contrast, grain number increased at a rate of 100 grains m⁻² yr⁻¹. Modern hybrids had larger panicle size and showed greater accumulation of WSC during vegetative period (as measured at the start of flowering) and greater remobilization of WSC during the reproductive period (after flowering) to grain, thus, maintaining grain size on the increased grain number per unit area and harvest index. These findings suggest that WSC dynamics play a critical role on past genetic yield gain in sorghum and its potential for future improvements should be considered.

中文翻译：

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美国商品高粱育种回顾性研究：二．与产量增加相关的生理变化

了解对产量的长期选择做出反应的生理变化可以为育种决策提供信息并加速遗传增益。本研究的目的是表征随时间变化的杂交种与不同发布年份的高粱（双色高粱）的产量相关生理性状的变化L. Moench）。田间试验于 2018 年和 2019 年在堪萨斯州和得克萨斯州的 8 个地点年内进行，其中包括 Pioneer 在 1963 年至 2017 年期间发布的 20 种市售高粱杂交种。在 2 个地点年内确定了与产量相关的详细生理特性包括生殖期的籽粒产量及其组成、籽粒灌浆、植物生物量、穗长和水溶性碳水化合物（WSC）。与使用历史产量数据的估计一致，高粱产量提高了 27 kg ha ^-1  yr ^-1。对于具有详细的产量相关生理特性的 2 个地点年，最终粒重、灌浆持续时间和随时间推移的速率没有变化。相比之下，晶粒数以每 100 粒米的速度增加⁻² 年⁻¹。现代杂交种具有更大的圆锥花序，并且在营养期（在开花开始时测量）显示出更多的 WSC 积累，并且在生殖期（开花后）WSC 对籽粒的再动员更多，因此，随着籽粒数量的增加保持籽粒大小单位面积和收获指数。这些发现表明，WSC 动力学对高粱过去的遗传产量增益起着关键作用，应考虑其未来改进的潜力。