Abstract
ABSTRACT Wheat (Triticum aestivum L.) production requires a large amount of nitrogen (N) supply because growers aim to achieve high grain yield and appropriate grain protein content simultaneously. A comprehensive understanding of the mechanisms that underpin efficient N usage at limited N in wheat can facilitate the development of new N-saving varieties in this major crop. Here, we performed comparative analysis of flag leaf responses to N availability in soft red winter wheat with contrasting N use efficiency (NUE); VA08MAS-369 (high NUE) and VA07W-415 (low NUE). This study demonstrated that accelerated senescence along with enhanced breakdown of protein and starch in flag leaves was correlated with higher grain yield, NUE for grain yield, and NUE for grain protein under N limitation. The more dramatic reductions in flag leaf N compounds and carbohydrate reserves in VA08MAS-369 were linked with significantly elevated expression of genes and enzymes associated with these metabolic pathways in this high NUE genotype. Consistent with the gene expression data, nitrate reductase, glutamine synthetase, and NAD-dependent glutamate dehydrogenase activities were highly induced under limited N in VA08MAS-369. It was previously reported that accelerated senescence contributes to increased grain protein content in wheat under regular N supply. This study provides molecular and physiological evidence that vigorous senescence and N remobilization also benefit grain yield under N deprivation.
Highlights
Wheat (Triticum aestivum L.) is the most widely grown crop, cultivated on 220 million ha worldwide (FAO Stat, 2016)
We grew two representative soft red winter wheat gen otypes with contrasting N use efficiency (NUE), VA08MAS-369 and VA07W415, under normal and low N conditions, and analyzed their grain yield, yield components, and NUErelated traits (Figure 1)
The results presented here demonstrated that acceler ated leaf senescence and nitrogen remobilization in flag leaves at the post-anthesis stage were associated with higher grain yield, NUE for grain yield (NUEY), and NUE for grain protein (NUEP) under N deprivation in soft red winter wheat
Summary
Wheat (Triticum aestivum L.) is the most widely grown crop, cultivated on 220 million ha worldwide (FAO Stat, 2016). Wheat requires a high level of nitrogen (N) appli cation relative to most other crops because growers aim to achieve both high yield and appropriate grain protein content. Due to its large cultivation area and N requirement, 18% of the total N fertilizers produced globally are applied to wheat, the largest amount of N supply in crop production (Ladha et al, 2016). The production cost of N-based fertilizers has constantly been rising. Improve ment of N use efficiency (NUE) in wheat reduces grower costs, and addresses the environmental issues caused by N runoff and denitrification in wheatgrowing regions.
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