Background and Aims

Climate change in the Mediterranean-climate region of Australia is reducing growing season rainfall and delaying first autumn rain or the onset of ‘autumn break’. We tested the hypothesis that selection for yield and agronomic traits has favored adaptation to early season drought in Australian wheat (Triticum aestivum L.).

Methods

Ten wheat varieties released between 1958 and 2012 were grown in a glasshouse. After sowing in dry soil, the equivalent of 25 mm rainfall was supplied, with no subsequent watering provided for 32 days to induce an early season drought treatment (ESD) while a well-watered treatment (WW) was planted on a wet soil that was water-saturated 48 h before sowing. We measured soil and plant water status, gas exchange, shoot and root traits at the end of drought (32 days after sowing) and at anthesis, and grain yield per plant at maturity.

Results

Grain yield increased with year of release at 0.43% yr^–1 under well-watered conditions and at 0.35% yr^–1 under drought. The improved yield under drought was associated with a shorter time to flowering, and a change from isohydric behavior (maintained Ψ_leaf, reduced g_s, leaf photosynthesis and transpiration rates in response to drought) in older varieties to anisohydric behavior (decreased Ψ_leaf and increased g_s, leaf photosynthesis and transpiration in response to drought) in newer varieties that reduced leaf area and maintained higher g_s, and higher photosynthesis per unit leaf area.

Conclusions

Direct selection for yield and agronomic traits between 1958 and 2012 has improved adaptation to early-season drought. Our collection of varieties is an interesting model to probe for variation in drought tolerance.

中文翻译：

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五个十年的产量选择有利于澳大利亚小麦对早季干旱的非等水和物候适应

背景和目标

澳大利亚地中海气候区的气候变化正在减少生长季节的降雨，并推迟第一场秋雨或“秋假”的到来。我们检验了产量和农艺性状的选择有利于澳大利亚小麦 ( Triticum aestivum L.) 适应早期干旱的假设。

方法

1958 年至 2012 年间发布的 10 个小麦品种在温室中种植。在干燥的土壤中播种后，提供相当于 25 毫米的降雨量，随后 32 天没​​有提供后续浇水以诱导早期干旱处理 (ESD)，而在湿润的土壤上种植了充分浇水的处理 (WW)。播前 48 h 水饱和。我们测量了干旱末期（播种后 32 天）和开花期的土壤和植物水分状况、气体交换、枝条和根系性状，以及成熟时的每株谷物产量。

结果

在水分充足的条件下，谷物产量随着释放年份的增加而增加 0.43% yr ^-1，在干旱条件下增加 0.35% yr ^{-1 。}干旱条件下产量的提高与开花时间的缩短有关，并且老品种的等水行为（保持 Ψ_叶、降低g _s、叶片光合作用和蒸腾速率以应对干旱）转变为等水行为（降低 Ψ_叶和增加g _s，叶片光合作用和蒸腾响应干旱）在减少叶面积并保持较高g _s和单位叶面积光合作用较高的新品种中。

结论

1958 年至 2012 年间对产量和农艺性状的直接选择提高了对早季干旱的适应能力。我们的品种集合是一个有趣的模型，用于探索耐旱性的变化。