Nitrogen Accumulation and Transport Characteristics and Grain Protein Content of Wheat Varieties with Different Nitrogen Efficiencies and Their Responses to Irrigation

[Objectives] To explore the differences in nitrogen accumulation and transport characteristics and grain protein content of wheat varieties with different nitrogen efficiencies and their responses to irrigation. [Methods] Under field conditions, using nitrogen-inefficient varieties Luohan 17 and Xinhua 818 and nitrogen-efficient varieties Bainong 418 and Bainong 419 as materials, this paper studied the nitrogen accumulation and transport characteristics, grain protein content and protein yield of wheat with different nitrogen efficiencies under rainfed and irrigated conditions. [Results] Compared with the nitrogen-inefficient wheat varieties, the pre-flowering nitrogen transport and the shoot nitrogen accumulation at the mature stage of nitrogen-efficient wheat varieties decreased by 15.08% and 28.25%, respectively, and the grain protein content decreased by 11.66%, under rainfed conditions. Compared with rainfed conditions, nitrogen accumulation in shoots of nitrogen-inefficient wheat varieties and nitrogen-efficient wheat varieties at the mature stage increased by 6.59% and 67.05%, respectively, and grain protein content decreased by 13.50% and 3.47%, respectively, under irrigated conditions. The two nitrogen efficiency types of wheat had different responses to irrigation after flowering. After irrigation, the nitrogen accumulation of nitrogen-efficient varieties increased by 274.80%, while that of nitrogen-inefficient varieties decreased by 51.15%. Finally, the grain protein yield of nitrogen-inefficient wheat varieties remained stable, while the grain protein yield of nitrogen-efficient wheat varieties increased by 40.37%. [Conclusions] The nitrogen accumulation and transport characteristics and grain protein content of wheat varieties with different nitrogen efficiencies are different under different irrigation conditions. In production, it is necessary to take different irrigation measures in accordance with the difference in nitrogen efficiency of wheat varieties, so as to increase the protein content of wheat grains.