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Grain yield (GY) and grain protein concentration (GPC) are two major targets in wheat breeding programs as these traits contribute to the economic value of the wheat crop. Unfortunately, their simultaneous improvement is hampered by the genetic negative GPC-GY relationship. It has been shown that the deviation to this relationship (“Grain Protein Deviation”, GPD) has a genetic basis and might be useful to shift this negative relationship but its biological bases remain unclear.

GPD was shown to be mainly related to the genetic variability for post-anthesis nitrogen (N) uptake (PANU) in the North-West European agro-climatic conditions.We proposed that the genetic variability for the access to N in the soil (root architecture and functioning) or for the regulation of PANU by the plant N status (N transport and assimilation) could explain GPD.

As delaying leaf senescence during the post-anthesis period might result in increasing PANU, we analysed the genetic determinants of the phenotypic relationships between leaf senescence duration after anthesis and GPC or GY using data obtained on a wheat mapping population grown in a large mutli-environment trial network. A positive association was found between leaf senescence duration and GPC or GY depending on the environment. We suggested that the impact of delaying leaf senescence after anthesis on GY or GPC might be modulated by the N availability during the post-anthesis period and would lead to modify the GPC-GY relationship depending on the considered environments.

Finally, data obtained on three connected mapping populations grown in a large mutlienvironment trial network were used to suggest by meta-QTL analysis potential genomic regions possibly useful in wheat breeding to improve GPC without reducing GY. This put forward genomic regions located on the 2A and 3B chromosomes as potentially interesting targets to improve GPC. In particular, the region on the 2A might be related to a chloroplastic glutamine synthetase gene previously shown to be associated with genetic variability for GPC in bread wheat..