Studies at a regional scale suggest that although maize (Zea mays L.) yield increased substantially, sensitivity to water deficit also increased concurrently with crop improvement. This study assessed changes in yield and yield stability after two decades of breeding by evaluating two cohorts of hybrids released by the AQUAmax program and comparing them to a non-AQUAmax control. Studies were conducted in 2019 and 2020 seasons at four sites under well-watered, moderate and severe stress conditions. Plant densities varied from 2.5 to 12.5 pl m−2. AQUAmax hybrids yielded more than non-AQUAmax hybrids under water deficit conditions with the magnitude of the difference dependent on plant density. The sensitivity in yield across environments with a wide range of total crop evapotranspiration (350–800 mm) was lower for AQUAmax than non-AQUAmax, so both yield and yield under stress conditions (yield stability), were enhanced for AQUAmax hybrids. The median differences between observed yields and the 80% quantile yield–evapotranspiration front were 379 for AQUAmax and 427 g m⁻² for non-AQUAmax hybrids. We conclude that deliberate selection of hybrids for yield performance under water deficit underpinned the sustained improvement in yield stability after two decades of drought breeding. Future research should focus on understanding the root causes for the suboptimal utilization of drought tolerant maize for the diversity of environments at a regional scale.

中文翻译：

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随着温带环境中玉米产量的增加，对水分亏缺的耐受性持续提高

区域范围内的研究表明，尽管玉米 ( Zea maysL.) 产量大幅增加，随着作物改良，对水分亏缺的敏感性也增加。本研究通过评估 AQUAmax 计划发布的两组杂交种并将它们与非 AQUAmax 对照进行比较，评估了经过二十年育种后产量和产量稳定性的变化。研究于 2019 年和 2020 年在水分充足、中度和重度胁迫条件下的四个地点进行。植物密度从 2.5 到 12.5 pl m−2 不等。在缺水条件下，AQUAmax 杂交种的产量高于非 AQUAmax 杂交种，差异的大小取决于植物密度。AQUAmax 在作物总蒸散量范围较广（350-800 毫米）的环境中对产量的敏感性低于非 AQUAmax，因此产量和胁迫条件下的产量（产量稳定性），增强了 AQUAmax 混合动力车。AQUAmax 和 427 gm 观察到的产量和 80% 分位数产量-蒸散前沿之间的中位数差异为 379^-2用于非 AQUAmax 杂种。我们的结论是，在缺水情况下有意识地选择具有产量表现的杂交种支持了经过二十年的干旱育种后产量稳定性的持续提高。未来的研究应侧重于了解耐旱玉米在区域范围内对环境多样性的次优利用的根本原因。