Crop improvement for Nitrogen Use Efficiency (NUE) requires a well-defined phenotype and genotype, especially for different N-forms. As N-supply enhances growth, we comprehensively evaluated 25 commonly measured phenotypic parameters for N response using 4 N treatments in six indica rice genotypes. For this, 32 replicate potted plants were grown in the green-house on nutrient-depleted sand. They were fertilized to saturation with media containing either nitrate or urea as the sole N source at normal (15 mM N) or low level (1.5 mM N). The variation in N-response among genotypes differed by N form/dose and increased developmentally from vegetative to reproductive parameters. This indicates survival adaptation by reinforcing variation in every generation. Principal component analysis segregated vegetative parameters from reproduction and germination. Analysis of variance revealed that relative to low level, normal N facilitated germination, flowering and vegetative growth but limited yield and NUE. Network analysis for the most connected parameters, their correlation with yield and NUE, ranking by Feature selection and validation by Partial least square discriminant analysis enabled shortlisting of eight parameters for NUE phenotype. It constitutes germination and flowering, shoot/root length and biomass parameters, six of which were common to nitrate and urea. Field-validation confirmed the NUE differences between two genotypes chosen phenotypically. The correspondence between multiple approaches in shortlisting parameters for NUE makes it a novel and robust phenotyping methodology of relevance to other plants, nutrients or other complex traits. Thirty-Four N-responsive genes associated with the phenotype have also been identified for genotypic characterization of NUE.

改善作物的氮利用效率（NUE）需要明确定义的表型和基因型，尤其是对于不同的N型。由于氮供应促进生长，我们使用6种in稻基因型的4种氮处理方法，全面评估了25种常用的表型参数对氮的响应。为此，在温室中养分贫瘠的沙子上种植了32具重复的盆栽植物。在正常（15 mM N）或低水平（1.5 mM N）的条件下，用含有硝酸盐或尿素作为唯一氮源的培养基施肥至饱和。基因型之间N响应的变化因N形式/剂量的不同而不同，并且从营养参数到生殖参数在发育上都增加。这表明通过加强每一代的变异来适应生存。主成分分析将营养参数与繁殖和发芽分开。方差分析表明，相对于较低水平，正常N促进发芽，开花和营养生长，但产量和NUE受限制。对最相​​关参数的网络分析，它们与产量和NUE的相关性，通过特征选择进行排名以及通过偏最小二乘判别分析进行验证，使得可以针对NUE表型列出八个参数。它包括发芽和开花，枝条/根长和生物量参数，其中六个是硝酸盐和尿素共有的。现场验证证实了表型选择的两种基因型之间的NUE差异。NUE入围参数的多种方法之间的对应关系使其成为与其他植物，营养素或其他复杂性状相关的新颖而强大的表型分析方法。