Abstract The introgression of awns as a source of photoassimilates during grain filling has received has long been of particular attention in wheat. Although the benefits for average grain weight (AGW) seem consistent, those for yield still remain unclear, and the causes for the improved AGW have not been examined. In this study we carried out three field experiments. In two of them, one in CIMMYT (Mexico) and the other in Lleida (Spain), we compared awned-awnless near isogenic lines (NILs) subjected to defoliation and degraining during the effective period of grain filling, whilst in another experiment we analysed the responses of modern cultivars to awn detachment 10 days after anthesis under two nitrogen levels. There were not consistent differences in yield between the awned-awnless NILs neither across the locations nor across genetic backgrounds. This lack of effect on yield was associated with a compensatory effect of the presence of awns on decreasing grain number while increasing AGW. The manipulation treatments did not consistently affect AGW neither in the NILs nor in the modern cultivars. Focusing on the responses of the NILs, firstly there were some statistically significant responses in AGW but they were both mostly very small and inconsistent between defoliation and degraining treatments as well as between genetic backgrounds. Secondly these responses failed to be consistently more noticeable in the awnless than in the awned lines (as expected if the presence of awns increases AGW through increasing photosynthetic capacity during grain filling). The increase on AGW due to the presence of awns seemed ascribed to both an indirect and a direct effect. The former would simply reflect the consequence of awns reducing grain number: this would naturally be the consequence of an increased failure of distal florets to become fertile which would have reduced the proportion of grains constitutively smaller as well. A direct true effect on the capacity of the grains to grow also emerged with the analysis of individual size of each particular grain for the awned-awnless NILs revealing a constitutively higher potential size in the awned NILs, even for the largest grains.

中文翻译：

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芒真的与小麦产量有关吗？有芒/无芒等基因系的性能及其对源汇操作的响应研究

摘要 作为灌浆过程中光同化物的来源，芒的基因渗入长期以来一直受到小麦的特别关注。尽管平均粒重 (AGW) 的益处似乎是一致的，但产量的益处仍不清楚，而且 AGW 改善的原因尚未研究。在这项研究中，我们进行了三个田间试验。在其中两个，一个在 CIMMYT（墨西哥）和另一个在莱里达（西班牙），我们比较了在籽粒灌浆有效期间遭受落叶和脱粒的无芒近等基因系 (NIL)，而在另一个实验中，我们分析了现代栽培品种在两种氮水平下对开花后10天芒脱落的反应。无论是跨位置还是跨遗传背景，有芒无芒 NIL 的产量都没有一致的差异。这种对产量没有影响的情况与芒的存在对减少谷物数量同时增加 AGW 的补偿作用有关。无论是在 NILs 还是在现代栽培品种中，操作处理都没有持续影响 AGW。关注 NIL 的响应，首先在 AGW 中存在一些统计上显着的响应，但它们大多非常小且在脱叶和脱粒处理之间以及遗传背景之间不一致。其次，这些反应在无芒线中并没有比在有芒线中更明显（正如预期的那样，如果芒的存在通过在灌浆过程中增加光合能力来增加 AGW）。由于芒的存在，AGW 的增加似乎归因于间接和直接影响。前者将简单地反映芒减少粒数的后果：这自然是远端小花无法受精的结果增加，这也会降低组成性较小的粒的比例。对有芒无芒 NIL 的每个特定谷物的个体尺寸的分析也显示了对谷物生长能力的直接真实影响，揭示了有芒 NIL 的组成性更高的潜在尺寸，即使对于最大的谷物也是如此。由于芒的存在，AGW 的增加似乎归因于间接和直接影响。前者将简单地反映芒减少粒数的后果：这自然是远端小花无法受精的结果增加，这也会降低组成性较小的粒的比例。对有芒无芒 NIL 的每个特定谷物的个体尺寸的分析也显示了对谷物生长能力的直接真实影响，揭示了有芒 NIL 的组成性更高的潜在尺寸，即使对于最大的谷物也是如此。由于芒的存在，AGW 的增加似乎归因于间接和直接影响。前者将简单地反映芒减少粒数的后果：这自然是远端小花无法受精的结果增加，这也会降低组成性较小的粒的比例。对有芒无芒 NIL 的每个特定谷物的个体尺寸的分析也显示了对谷物生长能力的直接真实影响，揭示了有芒 NIL 的组成性更高的潜在尺寸，即使对于最大的谷物也是如此。这自然是由于远端小花无法受精而增加的结果，这也会降低组成性较小的谷物比例。对有芒无芒 NIL 的每个特定谷物的个体尺寸的分析也显示了对谷物生长能力的直接真实影响，揭示了有芒 NIL 的组成性更高的潜在尺寸，即使对于最大的谷物也是如此。这自然是由于远端小花无法受精而增加的结果，这也会降低组成性较小的谷物比例。对有芒无芒 NIL 的每个特定谷物的个体尺寸的分析也显示了对谷物生长能力的直接真实影响，揭示了有芒 NIL 的组成性更高的潜在尺寸，即使对于最大的谷物也是如此。