Abstract Water is the main factor determining yield performance under drought conditions. Traditional soybean breeding has significantly increased grain yield under drought, but its effect on water use strategies and associated traits are not well understood. Field and pot experiments with new cultivars and landrace soybean genotypes were undertaken to identify the effect of soybean breeding on water use strategies and related leaf and root functional traits under different water regimes. The new cultivars, on average, had 33.9 %, 45.1 % and 169 % higher grain yields and 47.9 %, 98.4 % and 244 % higher water use efficiencies for grain yield (WUEG) but 8.8 %, 38.1 % and 19.6 % lower water use than the landraces in the field and pot experiments 1 and 2, respectively. Stomatal conductance decreased in the new cultivars at higher soil water contents than the landraces during soil drying. The new cultivars, on average, had a 22.9 % lower root fraction, 21.5 % lower leaf fraction, 20.6 % lower stem fraction and 69.8 % higher pod fraction than landraces, which had 21.7 % and 26.8 % lower root hydraulic conductance at the R2 and R6 stages, respectively, than the landraces. Our results show that (1) traditional soybean breeding has changed the water use strategy from profligate to conservative and improved yield performance and WUEG, (2) the high sensitivity of stomatal conductance to water stress is coordinated with lower root hydraulic conductance to limit water use, and (3) selecting new cultivars with high grain yield but low water use may a new way to improve yield performance under water-limited conditions.

中文翻译：

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传统大豆育种对干旱半干旱地区水分利用策略的影响

摘要 水分是决定干旱条件下产量表现的主要因素。传统的大豆育种在干旱条件下显着提高了粮食产量，但其对水分利用策略和相关性状的影响尚不清楚。对新品种和地方大豆基因型进行田间和盆栽试验，以确定大豆育种对不同水分条件下水分利用策略和相关叶和根功能性状的影响。平均而言，新品种的粮食产量分别提高了 33.9%、45.1% 和 169%，粮食产量用水效率（WUEG）分别提高了 47.9%、98.4% 和 244%，但用水效率分别提高了 8.8%、38.1% 和 19.6%。分别比田间和盆栽试验 1 和 2 中的地方品种。在土壤干燥期间，土壤含水量高于地方品种的新品种的气孔导度降低。平均而言，与地方品种相比，新品种的根分数降低了 22.9%，叶分数降低了 21.5%，茎分数降低了 20.6%，豆荚分数提高了 69.8%，后者在 R2 和 R2 处的根水导率分别降低了 21.7% 和 26.8%。 R6阶段，分别比地方种族。我们的结果表明 (1) 传统大豆育种已将水分利用策略从挥霍变为保守并提高了产量性能和 WUEG, (2) 气孔导度对水分胁迫的高敏感性与较低的根部水力导度相协调以限制水分利用(3) 选择高产低耗水的新品种可能是一种在缺水条件下提高产量性能的新途径。