Abstract: Drought is a major environmental stress that limits alfalfa (Medicago sativa L.) growth in northern China. Drought tolerance evaluation can provide reference for varieties selection. Here,we measured plant root-shoot ratio and analyzed proline content,soluble sugar content,soluble protein content,SOD activity,POD activity,CAT activity of four part of plants (leaf,stem,root collar,root) under two PEG6000-simulated drought levels (100,200 g L^-1). Results showed that plant biomass,plant height,leaf area and root length decreased while root-shoot ratio increased. Proline,soluble sugar and soluble protein contents increased with the increase of PEG content. Activity of SOD,POD and CAT showed the similar trends. Proline,soluble sugar and CAT activity are more responsive to drought stress. The responses of leaves to drought stress were less than those of stem and root. The responses of root collar proline and soluble sugar content to drought stress were the greatest among four organs. In the evaluation of varieties’ drought resistance,root soluble protein,root collar proline,root collar soluble sugar,root soluble sugar and root CAT activity accounted for a large proportion. When treated with 100 g·L^-1PEG,‘Gongnong No.1’,‘Zhongmu No.1’ and ‘Vision’ were more drought-resistant. When treated with 200 g·L^-1 PEG,‘2010’,‘Dongmu No.1’,‘Magna graze 2’ and ‘Spyder’ had strong drought resistance.

Key words: Alfalfa, Different organs, Drought resistance, Principal component analysis, Comprehensive evaluation

摘要： 为筛选抗旱性强的苜蓿（Medicago sativa L.）品种，本试验以12个苜蓿品种为材料，利用聚乙二醇（Polyethylene glycol，PEG-6000）模拟干旱处理，设置了100 g·L^-1和200 g·L^-1两个胁迫梯度，分别测定叶片、茎、根颈、根系4个器官的渗透调节物质含量、抗氧化酶活性和植株根冠比，通过主成分分析计算植株各器官生理指标在抗旱性评价过程中所占权重，结合抗旱系数评价苜蓿品种的抗旱性。结果表明，在100 g·L^-1和200 g·L^-1 PEG模拟干旱胁迫下，植株的生长受到抑制，生物量、株高、叶面积、根长均减小，根冠比增加；各器官脯氨酸、可溶性糖、可溶性蛋白含量增加；超氧化物歧化酶、过氧化物酶、过氧化氢酶活性提高；在所有的生理指标中，脯氨酸、可溶性糖、过氧化氢酶活性对干旱胁迫的响应较敏感。不同器官生理调节物质的抗旱系数存在差异，叶片各指标对干旱胁迫的响应小于茎和根系，根颈脯氨酸和可溶性糖含量对干旱胁迫的响应大于叶片、茎和根系。在评价品种抗旱性时，根系可溶性蛋白含量、根颈脯氨酸含量、根颈可溶性糖含量、根系可溶性糖含量及根系过氧化氢酶活性占权重较大。综合分析得出，100 g·L^-1 PEG处理时，‘公农1号’、‘中苜1号’和‘前景’的抗旱性比较强；200 g·L^-1PEG处理时，‘骑士2’、‘东苜1号’、‘巨能2’和‘斯贝德’的抗旱性较强，可作为苜蓿抗旱栽培的参考品种。

关键词: 苜蓿, 不同器官, 抗旱性, 主成分分析, 综合评价