Abstract: Nitrogen is an important nutrient element and restricts wheat growth and economic yield,  so screening and breeding low nitrogen tolerant wheat varieties is an effective way to improve nitrogen utilization rate and reduce production cost. In this study, 118 wheat varieties were grown in low nitrogen (0.1 mmol·L^-1) and normal nitrogen (5 mmol·L^-1)  conditions using hydroponic methods. Nitrogen efficiency of plants was measured based on 7 indicators about root dry weight, straw dry weight,  root/shoot ratio, plant dry weight, maximum root length, primary root number and secondary primary root. The low nitrogen tolerance of wheat varieties was evaluated by using fuzzy membership function method, principal component analysis and cluster analysis. The results showed that the root dry weight, root/shoot ratio and primary root number of wheat seedlings significantly increased, the stem and leaf dry weight, plant dry weight and maximum root length decreased in different degrees under low nitrogen stress, and the 7 seedling traits were significantly different at the two nitrogen levels. Three principal components were extracted by principal component analysis, and the contribution rate was 43.575%, 22.904% and 17.873%, respectively. The cumulative contribution rate reached to 84.351%. 118 wheat varieties were divided into 5 categories (strong resistance to low nitrogen, resistance to low nitrogen, medium resistance to low nitrogen, nitrogen sensitive, and nitrogen highly sensitive) according to the D value of comprehensive evaluation of low nitrogen tolerance. Qida 195, Jinfeng 7183 and Tianmin 198 were identified as low nitrogen tolerant wheat varieties. Two varieties (Shannong 0917 and Lumai 8) with relatively strong low nitrogen tolerance were screened. There were some obviously differences in the low nitrogen tolerance mechanisms of different wheat varieties. The research results provided theoretical and material basis for breeding of wheat varieties with low nitrogen resistance.

Key words: wheat, low nitrogen resistance, fuzzy membership function method, principal component analysis, cluster analysis

摘要： 氮素作为重要的营养元素，限制着小麦的生长发育和经济产量，筛选和培育耐低氮小麦品种是提高氮素利用率、降低生产成本的有效途径。以118份不同基因型小麦为材料，在低氮(0.1 mmol·L^-1)和正常氮(5 mmol·L^-1)条件下苗期水培，测定根干重、茎叶干重、根冠比、植株干重、最大根长、初生根数和二级初生根数等相关指标，采用模糊隶属函数法、主成分分析以及聚类分析法综合评价小麦品种的耐低氮性。结果表明，在低氮胁迫下小麦幼苗的根干重、根冠比和初生根数目显著提高，茎叶干重、植株干重和最大根长不同程度的降低，7个苗期性状指标在两个氮水平下均存在显著性差异。主成分分析提取3个主成分，贡献率分别为 43.575%、22.904%和17.873%，累积贡献率达 84.351%。以耐低氮性综合评价D值进行聚类分析，将118份小麦品种划分为强耐低氮型、耐低氮型、中间型、较敏感型和敏感型5类。筛选出3份耐低氮型小麦（齐大195、金丰7183和天民198）和2份强耐低氮型小麦（山农0917和鲁麦8号）。不同小麦品种的耐低氮机制不同，研究结果为小麦耐低氮品种的选育提供理论依据和材料基础。

关键词: 小麦, 耐低氮性, 模糊隶属函数法, 主成分分析, 聚类分析