During a century of maize (Zea mays L.) breeding, yield genetic gain was largely determined by increased reproductive resilience under stress and establishment of sink size (number of grains per unit area). Considering grains as competing sinks for C and N assimilates, understanding changes in the C and N economy can provide insights to define selection criteria towards a sustained yield improvement. A cognitive framework to define such criteria may consist in connecting the water‐soluble carbohydrates (WSC) and N dynamics in stem and leaves with the reproductive sink strength during post‐flowering. The objectives of this study were to advance such framework by (a) quantifying grain N demand and remobilization capacity in two hybrids as affected by N availability, and (b) formalizing how the interplay between N and WSC remobilization influence grain growth. Single cross hybrids 3394 and P1197 (released in 1991 and 2014) were evaluated to represent keystone phases of germplasm development (conventional and molecular breeding eras). P1197 outyielded 3394 consistently under high N supply, and its better N utilization efficiency was reflected through a lower grain N concentration. Under high N, the ability to maintain a greater leaf area during late grain‐filling for P1197 resulted in a reduced leaf N remobilization. Although yield was not limited by C supply, 3394 exposed greater remobilization of WSC during late grain‐filling. This study contributes to advance the development of a relevant C to N framework to further analyze drivers of genetic yield gain and assist in selection strategies in maize.

中文翻译：

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整合氮和水溶性碳水化合物在玉米中的动态：不同年代杂种的比较

在玉米的世纪（玉米L.）育种，产量遗传增益在很大程度上取决于胁迫下的生殖抗逆力的提高和汇大小（单位面积谷物的数量）的确定。考虑到谷物是碳和氮同化物的竞争性吸收者，了解碳和氮经济的变化可以提供洞见，以定义选择标准，从而持续提高产量。定义此类标准的认知框架可能包括将花后的茎和叶中的水溶性碳水化合物（WSC）和N动态与生殖下沉强度联系起来。这项研究的目的是通过（a）量化受氮素有效性影响的两个杂种中的氮素需求量和转运能力，以及（b）规范氮素和WSC转运之间的相互作用如何影响谷物生长，来改善这种框架。评价了单杂交种3394和P1197（分别于1991和2014年发布）以代表种质发育的关键阶段（常规和分子育种时代）。在高氮供应下，P1197的产量始终稳定地达到3394，其较低的籽粒氮浓度反映了其较高的氮利用效率。在高氮下，P1197在后期灌浆过程中保持较大叶片面积的能力导致叶片氮的迁移减少。尽管产量不受碳供应的限制，但3394在后期灌浆期间暴露了更多的WSC迁移。这项研究有助于推动相关的C到N框架的发展，以进一步分析遗传产量增加的驱动因素并协助玉米的选择策略。