Durum wheat cultivars grown in Mediterranean environments can combine high grain nitrogen content with high grain yield

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.