Low temperature during the critical period of wheat can cause floret sterility, grain abortion, yield reduction, and economic losses. We tested the hypothesis that selection for yield improved frost tolerance. We measured phenology, yield and its components, including the distribution of grains within the spike, in a factorial experiment combining 12 wheat varieties released from 1973 to 2015, two sowing dates (mid-April and early or mid-May), two thermal regimes, ambient control and frost-protected, and two seasons. To protect crops from frost we used moveable, lightweight passive heating chambers before each frost event (≤ 0 °C). The rate of genetic gain in yield aligned with frost severity: it ranged from negligible under severe frost to 0.79 ± 0.05% y in unfrosted crops. The chambers diminished but did not fully prevent frost; across sources of variation grain yield was 179 ± 20.1 g m in ambient control and 264 ± 13.3 g m in frost-protected treatments. Frost intensity was calculated as the cumulative, canopy-level minimum temperature below 2 °C during the period from −300 to + 100 °C d centred at anthesis. For the pooled data, yield declined with frost intensity at 1.24 ± 0.12% °C. Across varieties and environments, frost-protected crops set 29 ± 3.0 grains spike compared with 19 ± 2.7 in ambient control. We did not find random grain abortion within spikelets, but random sterile spikelets. Average grain weight (weighed by the relative contributions of these grains to the number of grains per spike) in main shoot spike did not vary with thermal regime. Selection for yield did not improve frost tolerance. Preventing spring radiation frost improved spike fertility by increasing the proportion of grains in distal positions with no reduction in grain weight potential within spikelets in relation to controls. We advanced damage functions relating yield and frost, which are useful for modelling, and maps of grain set in spikes that help understanding the physiology of yield in response to frost.

中文翻译：

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一组历史小麦品种对霜冻的产量反应

小麦关键期低温会造成小花不育、籽粒败育、减产、经济损失。我们测试了产量选择提高了抗冻性的假设。我们在一项析因实验中测量了物候、产量及其组成部分，包括穗内谷物的分布，该实验结合了 1973 年至 2015 年发布的 12 个小麦品种、两个播种日期（四月中旬和五月初或中旬）、两种热状况，环境控制和防冻，以及两个季节。为了保护农作物免受霜冻影响，我们在每次霜冻事件（≤ 0 °C）之前使用了可移动的轻型被动加热室。产量的遗传增益率与霜冻严重程度相关：从严重霜冻下可忽略不计到未霜冻作物中的 0.79 ± 0.05% y 不等。房间缩小了，但并没有完全防止霜冻；各种变异源中，环境控制下的谷物产量为 179 ± 20.1 g/m，霜冻处理下的谷物产量为 264 ± 13.3 g/m。霜冻强度计算为以花期为中心的 -300 至 + 100 °C 期间冠层最低温度累积低于 2 °C。对于汇总数据，在 1.24 ± 0.12% °C 的霜冻强度下，产量下降。在各个品种和环境中，受霜冻保护的作物颗粒数增加了 29 ± 3.0，而环境对照作物的颗粒数为 19 ± 2.7。我们没有发现小穗内随机的谷物败育，而是随机的不育小穗。主芽穗中的平均粒重（通过这些谷物对每个穗粒数的相对贡献来衡量）不随热状况而变化。产量选择并没有提高抗冻性。预防春季辐射霜通过增加远端位置的谷粒比例来提高穗肥力，而与对照相比，小穗内的谷粒重量潜力没有减少。我们改进了与产量和霜冻相关的损伤函数，这对于建模很有用，并且还提出了穗状谷物图，有助于理解产量对霜冻的反应的生理学。