Crop avoidance and tolerance strategies are critical adaptive mechanisms of drought stress and play different roles in grain yield. However, little is known about the contribution of these two mechanisms to grain yield in old and modern wheat genotypes. Here, pot and field experiments were carried out to characterize and compare the mechanisms of drought avoidance and drought tolerance, and determine their differential contributions to the yield in six wheat genotypes. The pot experiment results demonstrated that the old genotypes acquired a better avoidance ability to adapt to drought stress. These avoidance abilities include larger root systems, lower leaf areas, low stomatal conductance, pale green leaf colour, higher degrees of leaf rolling and leaf waxiness. The modern genotypes displayed stronger drought tolerance advantages, such as high osmotic adjustment and antioxidant enzyme activity, and a smaller root system. Our field experiment further showed that under severe water-deficit conditions, the old genotypes with stronger drought avoidance traits had higher yields and water use efficiency (WUE_g), whereas the modern genotypes with strong drought tolerance characteristics produced higher yields and had higher WUE_g under mild and intermediate water deficits. The results indicate that the relative contribution of drought tolerance and drought avoidance to grain yield depends to a large extent on the degree of drought stress and genotypes. Understanding the differential plant response depending on genotype and drought stress may help plant breeders develop drought-resistant varieties suitable for drought-prone environments under anticipated climate change scenarios.

中文翻译：

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干旱避免和耐旱性对旱地小麦种植产量提高的不同贡献

作物避免和耐受策略是干旱胁迫的关键适应机制，在粮食产量中发挥着不同的作用。然而，关于这两种机制对古老和现代小麦基因型谷物产量的贡献知之甚少。在这里，进行了盆栽和田间试验，以表征和比较避免干旱和耐旱的机制，并确定它们对六种小麦基因型产量的不同贡献。盆栽试验结果表明，老基因型获得了更好的适应干旱胁迫的回避能力。这些回避能力包括较大的根系、较低的叶面积、较低的气孔导度、淡绿色的叶片颜色、较高的叶片卷曲度和叶片蜡质。现代基因型表现出更强的耐旱优势，例如高渗透调节和抗氧化酶活性，以及​​较小的根系。我们的田间试验进一步表明，在严重缺水条件下，具有较强抗旱性状的老基因型具有较高的产量和水分利用效率（WUE_g )，而具有强耐旱性特征的现代基因型在轻度和中度缺水条件下产生更高的产量和更高的 WUE _{g 。}结果表明，耐旱性和避旱性对粮食产量的相对贡献在很大程度上取决于干旱胁迫程度和基因型。了解取决于基因型和干旱胁迫的不同植物反应可能有助于植物育种者在预期的气候变化情景下开发适合干旱易发环境的抗旱品种。