Breeders successfully increased US soybean [Glycine max (L.) Merr.] yields over the past nearly 100 years and altered various plant characteristics underpinning the yield gains. However, the impact of breeding on plant‐level water‐use efficiency (WUEp) has not been examined yet. This study, conducted across eight environments using maturity group IV cultivars released between 1930 and 2005, aimed to (1) determine if soybean WUEp, assessed using C isotope composition (δ13C) measurements on shoot biomass sampled at early seed filling (R5), has changed with cultivar year of release (YoR), and (2) assess how canopy temperature (CT) and WUEp relate to each other and to seed yield. Across environments and cultivars, δ13C ranged from −27.52‰ to −28.24‰ and the correlation between cultivar YoR and WUEp was positive in four individual environments (p ≤ 0.07), as well as across the eight environments (p = 0.0083), with an average increase of shoot δ13C of 0.004‰ per year of soybean breeding. Lower average δ13C values for specific environments were associated with higher precipitation prior to biomass sampling, which is consistent with a lower WUEp when more water was available. Interestingly, across environments, midday CT at early seed filling was negatively correlated with YoR and WUEp, suggesting that intrinsic WUE of more recently released cultivars was lower during high demand periods. Further studies are needed to understand the mechanisms underlying these relationships between WUEp and CT and to identify physiological mechanisms that can be targeted for breeding high‐yielding cultivars while increasing or maintaining WUEp.

中文翻译：

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大豆水分利用效率在 80 年的育种中得到提高


在过去的近 100 年里，育种者成功地提高了美国大豆 [Glycine max （L.） Merr.] 的产量，并改变了支撑产量增长的各种植物特性。然而，育种对植物水平水分利用效率 （WUEp） 的影响尚未得到检验。这项研究使用 1930 年至 2005 年间发布的成熟组 IV 品种在八个环境中进行，旨在 （1） 确定使用 C 同位素组成 （δ13C） 测量对早期种子填充 （R5） 采样的芽生物量进行评估的大豆 WUEp 是否随品种发布年份 （YoR） 而变化，以及 （2） 评估冠层温度 （CT） 和 WUEp 如何相互关联以及与种子产量的关系。在不同环境和品种中，δ13C 范围为 -27.52‰ 至 -28.24‰，品种 YoR 和 WUEp 之间的相关性在四个单独的环境中呈正相关 （p ≤ 0.07） 以及八个环境 （p = 0.0083），大豆育种每年芽 δ13C 平均增加 0.004‰。特定环境的平均 δ13C 值较低，与生物量采样前的降水量较高相关，这与可用水量较多时 WUEp 较低一致。有趣的是，在整个环境中，早期种子填充时的正午 CT 与 YoR 和 WUEp 呈负相关，这表明在高需求时期，最近发布的品种的内在 WUE 较低。需要进一步的研究来了解 WUEp 和 CT 之间这些关系的潜在机制，并确定可以靶向培育高产品种同时增加或维持 WUEp 的生理机制。