Abstract: Soil salinization seriously restricts the development of agricultural production， sustainable utilization of land resources， and ecological environment stability. To explore the evaluation methods and key indicators of alkali tolerance at germination stage of alfalfa （Medicago sativa L.） and screen the excellent germplasms， seeds of 57 cultivars were used as materials. Changes of nine seed germination and early seedling growth indicators， such as germination percentage， seedling percentage， etc.， were measured under control （distilled water） and alkaline （35 mmol·L^-1 NaHCO₃） conditions. The alkali tolerance coefficient， comprehensive alkali tolerance coefficient， principal component analysis and stepwise regression analysis were used for comprehensive evaluation and key indicators screen of alkali tolerance during alfalfa seed germination. Results revealed that the nine seed germination and seedling growth indicators showed a downward trend after NaHCO₃ treatment， and there were differences in response to alkali treatment. Based on the alkali tolerance D value and systematic clustering analysis， the alkali tolerance of 57 alfalfa cultivars was divided into three levels， namely， strong， medium， and weak， among which the alkali tolerance of ‘Bara520YQ’ and ‘Kehan’ were respectively the strongest and the weakest. The mathematical model of stepwise regression analysis indicated that root length， seedling percentage， shoot length， germination percentage， and seedling vigor index could be used as important indicators to evaluate the alkali tolerance of alfalfa during seed germination. This study provided excellent parental materials for the screening of strong alkali tolerant cultivars of alfalfa， the mining of key candidate genes， and the creation of new germplasm， and also laid a theoretical foundation for its cultivation and utilization.

Key words: Alfalfa, Seed germination, Alkali tolerance, Membership function, Cluster analysis, Comprehensive evaluation

摘要： 土壤盐碱化严重制约了农业生产发展、土地资源可持续利用和生态环境稳定。为探讨紫花苜蓿（Medicago sativa L.）种子萌发期耐碱性评价方法与关键指标，并筛选强耐碱性优异种质，本研究选用57个品种的种子，比较对照组（蒸馏水）和处理组（35 mmol·L^-1 NaHCO₃）条件下9个种子萌发与早期幼苗生长指标（发芽率、成苗率等）的变化。采用耐碱系数、综合耐碱系数、主成分分析、逐步回归分析综合评价苜蓿种子萌发期耐碱性并筛选评价关键指标。结果表明，NaHCO₃处理后，9个种子萌发与幼苗生长指标均呈下降趋势，且对碱响应存在差异。耐碱性D值和系统聚类分析将57个品种耐碱性划分为强、中、弱3个等级，其中，‘Bara520YQ’耐碱性最强、‘可汗’耐碱性最弱。逐步回归分析模型表明，根长、成苗率、苗长、发芽率和幼苗活力指数可作为评价紫花苜蓿种子萌发期耐碱性的重要指标。本研究为紫花苜蓿强耐碱性品种筛选、关键候选基因挖掘及新种质创制提供优异亲本材料，也为其栽培利用奠定理论基础。

关键词: 紫花苜蓿, 种子萌发, 耐碱性, 隶属函数, 聚类分析, 综合评价