Increased application of nitrogen fertilizers has significantly raised grain yield and protein concentration in wheat. However, only 30–50% of applied fertilizer nitrogen are usually utilized by the plant. In this study, four soft red winter wheat genotypes (Triticum aestivum L., IL07-4415, MD05W10208-11-8, OH06-150-57 and Sisson) were grown under three different nitrogen regimes (high, medium, and low) in a greenhouse, and grain yield, grain protein concentration, nitrogen use efficiency (NUE) and their associated traits were evaluated. Among the four genotypes, a high-yielding cultivar, Sisson, exhibited superior performance in terms of grain weight plant−1 and NUE for yield (NUEY) at low nitrogen due to maintained grain number spike−1 and harvest index. Significant yield losses due to nitrogen limitation were attributable to reduced spike number plant−1 and grain number spike−1 in the other genotypes. Interestingly, a linear relationship between NUEY and NUE for grain protein (NUEP) was detected at high (R2 = 0.67) and low (R2 = 0.42) nitrogen; both of these traits were positively correlated with grain number spike−1, 1000-seed weight, and harvest index under nitrogen-limited conditions (R2 = 0.35–0.48). These results suggest that simultaneous improvement of NUEY and NUEP could be achieved through the selection of the three yield components (grain number spike−1, 1000-seed weight, and harvest index) at low nitrogen.
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- Triticum aestivum
- nitrogen deficiency
- nitrogen use efficiency