Optimizing assimilate partitioning to wheat grains is important to improve grain size and filling. Manipulation of gene expression of assimilate transporters is promising to improve uptake capacity and partitioning. The barley sucrose transporter has been ectopically expressed in winter wheat controlled by the barley promoter (HOSUT lines). In greenhouse experiments, HOSUT lines produced lager grains and higher grain yields than the untransformed control cultivar ‘Certo’. This study aimed to evaluate and verify the potential of three HOSUT lines regarding grain yield and quality under field conditions. A three-year field trial in Switzerland using up to three N fertilization levels was performed. In addition to the three HOSUT lines and ‘Certo’, three Swiss reference lines were tested. Yield parameters, grain composition, phenology and disease scores were recorded. Grain weight was increased for HOSUT lines by 3–8 % compared to wildtype ‘Certo’, whereas grain number per spike was reduced by 4–12 %. Thus overall, grain yield per area remained largely unchanged. However, higher levels of iron and zinc found in HOSUT grains could be health-promoting. No negative unintended effects on chemical composition, disease susceptibility, and plant phenology were detected, with the exception of complete anther retention in one of the three HOSUT lines. While stimulation of sucrose uptake and/or partitioning in HOSUT lines resulted in higher grain size, an increase of total grain yield may only be achieved if trade-offs between grain size and grain number are overcome. The study contributes to the understanding of sucrose transporter modifications in wheat. It demonstrates the importance of field-testing crop plants that exhibit promising traits under controlled environments. More research is needed to identify the bottlenecks that appear under field conditions to unlock the potential of the HOSUT strategy for agronomic application.

中文翻译：

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田间试验揭示了异位表达大麦蔗糖转运蛋白的小麦籽粒大小和籽粒数量之间的权衡


优化小麦籽粒的同化物分配对于改善籽粒大小和灌浆非常重要。操纵同化物转运蛋白的基因表达有望提高摄取能力和分配。大麦蔗糖转运蛋白已在受大麦启动子（HOSUT 系）控制的冬小麦中异位表达。在温室实验中，HOSUT 品系比未转化的对照品种“Certo”生产更大的谷物和更高的谷物产量。本研究旨在评估和验证三个 HOSUT 品系在田间条件下谷物产量和质量的潜力。在瑞士进行了一项为期三年的田间试验，使用了三种施氮水平。除了三个 HOSUT 线和“Certo”之外，还测试了三个瑞士参考线。记录产量参数、谷物成分、物候和疾病评分。与野生型“Certo”相比，HOSUT 品系的粒重增加了 3-8%，而每穗粒数减少了 4-12%。因此，总体而言，粮食单位面积产量基本保持不变。然而，HOSUT 谷物中铁和锌含量较高可能有益于健康。除了三个 HOSUT 品系之一的花药完全保留之外，没有检测到对化学成分、疾病易感性和植物物候学的负面影响。虽然 HOSUT 系中蔗糖吸收和/或分配的刺激导致了更大的颗粒尺寸，但只有克服颗粒尺寸和颗粒数量之间的权衡，才能实现颗粒总产量的增加。该研究有助于了解小麦中蔗糖转运蛋白的修饰。它证明了在受控环境下表现出有希望的性状的田间测试作物的重要性。 需要更多的研究来确定田间条件下出现的瓶颈，以释放 HOSUT 策略在农艺应用中的潜力。