Relationships between Nitrogen Utilization and Grain Technological Quality in Durum Wheat: I. Nitrogen Translocation and Nitrogen Use Efficiency for Protein.

Durum wheat (Triticum durum Desf.) is widely cultivated in the Mediterranean area where plants generally suffer from water stress during grain-filling period. This study was conducted to evaluate the influence of N levels and water regimes on N translocation and nitrogen use efficiency for protein (NUEP) in durum wheat grown under Mediterranean conditions. A 2-yr experiment was performed in southern Italy using four cultivars, two water regimes (irrigated and rainfed) and three N levels (0, 60, and 120 kg ha^-1). Among the cultivars under study, Simeto showed the highest N translocation in both years and, together with of anto, also the highest NUEP values, especially in rainfed condition. This highlights their good adaptability to dry southern Italy environment. Nitrogen fertilization caused a general decrease of NUEP and its components in both growing seasons; this was more evident in the first drier year, mainly due to a decrease in N uptake. Under water Stress the higher N level caused a decrease in N translocation, N translocation efficiency, and grain N content. The contribution of translocated N to grain N content was 75% in the wetter year and 57% in the drier year, showing that in drought condition preanthesis N assimilation was lower. In conclusion under water stress condition the higher N level (120 kg ha^-1), despite determining an increase in plant N content, did not imply an increase in grain N content, due to a decrease in N translocation and efficiency. [ABSTRACT FROM AUTHOR]