Nitrogen (N) is one of the most important macronutrients for crop growth and development. Large amounts of N fertilizers are applied exogenously to improve grain yield and quality, which has led to environmental pollution and high cost of production. Therefore, improvement of N use efficiency (NUE) is a very important aspect for sustainable agriculture. Here, a pilot experiment was firstly conducted with a set of barley genotypes with confirmed NUE to validate the fast NUE screening, using chlorate as an analogue to nitrate. High NUE genotypes were susceptible to chlorate-induced toxicity whereas the low NUE genotypes were tolerant. A total of 180 barley RILs derived from four parents (Compass, GrangeR, Lockyer and La Trobe) were further screened for NUE. Leaf chlorosis induced by chlorate toxicity was the key parameter observed which was later related to low-N tolerance of the RILs. There was a distinct variation in chlorate susceptibility of the RILs with leaf chlorosis in the oldest leaf ranging from 10 to 80%. A genome-wide association study (GWAS) identified 9 significant marker-trait associations (MTAs) conferring high chlorate sensitivity on chromosomes 2H (2), 3H (1), 4H (4), 5H (1) and Un (1). Genes flanking with these markers were retrieved as potential targets for genetic improvement of NUE. Genes encoding Ferredoxin 3, leucine-rich receptor-like protein kinase family protein and receptor kinase are responsive to N stress. MTA4H5468 which exhibits concordance with high NUE phenotype can further be explored under different genetic backgrounds and successfully applied in marker-assisted selection.

氮（N）是作物生长和发育最重要的常量营养素之一。为了提高粮食产量和品质，大量外施氮肥，导致环境污染和生产成本较高。因此，提高氮素利用效率（NUE）是可持续农业的一个非常重要的方面。在这里，首先使用氯酸盐作为硝酸盐的类似物，对一组已确认 NUE 的大麦基因型进行了初步实验，以验证快速 NUE 筛选。高 NUE 基因型对氯酸盐诱导的毒性敏感，而低 NUE 基因型则具有耐受性。进一步筛选了来自四个亲本（Compass、GrangeR、Lockyer 和 La Trobe）的 180 个大麦 RIL 的 NUE。氯酸盐毒性引起的叶片失绿是观察到的关键参数，后来与 RIL 的低氮耐受性相关。RIL 的氯酸盐敏感性存在明显变化，最老的叶子​​出现叶黄化，变化范围为 10% 至 80%。全基因组关联研究 (GWAS) 确定了 9 个显着的标记性状关联 (MTA)，赋予染色体 2H (2)、3H (1)、4H (4)、5H (1) 和 Un (1) 对氯酸盐的高敏感性。侧翼带有这些标记的基因被检索为 NUE 遗传改良的潜在目标。编码铁氧还蛋白 3、富含亮氨酸的受体样蛋白激酶家族蛋白和受体激酶的基因对氮胁迫有反应。MTA4H5468表现出与高NUE表型的一致性，可以在不同遗传背景下进一步探索并成功应用于标记辅助选择。