Grain protein percentage is one of the main determinants of durum wheat grain quality. However, high grain protein percentages are generally associated with low grain yields. Our aim was to identify the genotypic constraints to the realization of high grain yields with high grain nitrogen contents. To investigate this relationship, four cultivars specifically selected for their large range in ‘grain yield-grain protein’ relationship were compared across three seasons in a Mediterranean environment at three nitrogen (N) fertilization rates (0, 80 and 160 kg N ha⁻¹). The genotypic superiority in protein percentage was consistently associated with lower number of grains m⁻² and high grain weight across years, N treatments and yield levels (from 3.5 to 8.5 t ha⁻¹), whereas grain yield ranking varied with year and N treatment. A high and consistent grain protein percentage was the consequence of a high N uptake by anthesis (250 kg N ha⁻¹ at the higher N rate) and was consistently associated to a low grain yield. The good capacity to absorb N after anthesis, on the contrary, resulted in a grain N percentage less reliable than that obtained through a high pre-anthesis N uptake, but still high and associated with the ability to make the most of favourable weather conditions by combining a high grain N with a grain yield comparable to those of more productive cultivars. Post-anthesis N uptake and high potential grain weight are two interesting targets in breeding for high yielding, high protein cultivars.

籽粒蛋白质百分比是硬粒小麦籽粒品质的主要决定因素之一。然而，高谷物蛋白质百分比通常与低谷物产量有关。我们的目的是确定实现高谷物氮含量的高产量的基因型限制。为了研究这种关系，在地中海环境中以三种氮 (N) 施肥率（0、80 和 160 kg N ha ^-1）。蛋白质百分比的基因型优势始终与较低的粒数 m ^-2和较高的粒重、N 处理和产量水平（从 3.5 到 8.5 t ha ^-1），而谷物产量排名随年份和 N 处理而变化。高且一致的谷物蛋白质百分比是开花期高 N 吸收的结果（在较高 N 速率下为 250 kg N ha ^-1），并且始终与低谷物产量相关。相反，开花后良好的氮吸收能力导致谷物氮百分比的可靠性低于通过高的开花前氮吸收获得的百分比，但仍然很高，并且与充分利用有利天气条件的能力有关将高谷物 N 与与高产栽培品种相媲美的谷物产量相结合。花后氮吸收和高潜在粒重是高产、高蛋白品种育种的两个有趣目标。