Abstract: With 120 wheat germplasms as materials，PEG6000 solution was used to simulate drought stress at seedling stage.Plant height，root length，fresh weight of shoot，dry weight of shoot，fresh weight of root，dry weight of root，root⁃shoot ratio and SPAD value were determined，and their drought tolerance coefficients were calculated.Principal component analysis（PCA）was performed based on their drought tolerance coefficients，cluster analysis was conducted using the comprehensive drought tolerance value（D），and comprehensive evaluation of drought tolerance of wheat germplasms was carried out.Highly drought⁃tolerant and drought⁃sensitive germplasms were selected to determine H₂O₂，malondialdehyde（MDA），proline（Pro），soluble sugar（SS）contents and catalase（CAT）activity，so as to analyze the physiological regulatory mechanism of drought tolerance.The pre⁃experiment confirmed that 25% was the optimal PEG6000 concentration，all phenotypic traits showed extremely significant difference compared with the control under this concentration. Drought stress obviously decreased fresh weight of shoot，dry weight of shoot，and SPAD value，but increased root length and root⁃shoot ratio.The correlations among phenotypic traits changed obviously under drought stress compared with those under normal water condition. Under drought stress，the correlation between root length and dry weight of shoot disappeared，SPAD value was significantly positively correlated with plant height and fresh weight.Genotype，drought and their interaction had extremely significant effects on all eight phenotypic traits.PCA showed that the first four principal components accounted for 86.67% of the total variation.The drought tolerance coefficients of all traits were extremely significantly positively correlated with D value，among which the correlation coefficients between drought tolerance coefficients of fresh weight of shoot，dry weight of shoot，fresh weight of root，dry weight of root and D value were higher， which were core indexes for drought tolerance identification. Cluster analysis based on D value showed that the wheat germplasms were divided into five groups，and 15 highly drought⁃tolerant germplasms were screened out，including Xinong 109，Luohan 22，Shannong 116，Xinmai 26，Yu’an X208，Bainong 207，Luyuan 502，Bainong 4199，Xinmai 60，Xinong 519，Wenmai 801，Saidemai 8，Yunong 186，Xinong 20，and Fengdecun 20.Compared with highly drought⁃sensitive germplasms， highly drought⁃tolerant germplasms had significantly lower H₂O₂ and MDA contents，and significantly higher CAT activity，Pro and SS contents，and CAT activity，Pro and SS contents were significantly or extremely significantly positively correlated with D value，indicating that highly drought⁃tolerant germplasms alleviate drought damage by enhancing CAT activity，accumulating Pro and SS，and reducing H_₂O_₂ and MDA accumulation.

Key words: Wheat, Germplasm resources, Seedling stage, Drought tolerance, Comprehensive evaluation, Physiological regulation

摘要： 以120份小麦种质为试验材料，利用 PEG6000溶液模拟干旱胁迫，测定株高、根长、地上部鲜质量、根鲜质量、地上部干质量、根干质量、根冠比、SPAD值，计算其耐旱系数，并基于表型性状耐旱系数进行主成分分析，然后通过耐旱性综合评价值（D）进行聚类分析，综合评价小麦种质苗期耐旱性，最后选取高耐旱种质和高敏旱种质测定其干旱胁迫条件下的过氧化氢（H₂O₂）、丙二醛（MDA）、脯氨酸（Pro）、蔗糖（SS）含量及过氧化氢酶（CAT）活性，分析其耐旱生理调控机制。结果表明，通过预试验确定小麦苗期耐旱性鉴定的最佳PEG6000溶液质量分数为25%，该质量分数下各表型性状与未干旱处理间差异均达到极显著水平。干旱胁迫处理后，小麦种质地上部鲜质量、地上部干质量及SPAD值均大幅下降，根长、根冠比均明显升高。相关性与方差分析显示，干旱胁迫条件下表型性状间的相关性较正常水分条件下发生明显改变，其中，根长与地上部干质量的相关性消失，SPAD 值与株高、根鲜质量均呈极显著正相关；基因型、干旱及二者互作对8个表型性状均产生极显著影响。基于表型性状耐旱系数的主成分分析表明，前4个主成分的累计贡献率达86.67%。8个表型性状的耐旱系数与D值均呈极显著正相关，其中，地上部鲜质量、根鲜质量、地上部干质量、根干质量的耐旱系数与D值的相关系数较高，可作为小麦苗期耐旱性鉴定的核心指标。基于D值的聚类分析表明，供试材料可划分为5个组，筛选出高耐旱种质15份，包括西农109、洛旱22、山农116、新麦26、豫安X208、百农207、鲁原502、百农4199、新麦60、西农519、温麦801、赛德麦8、豫农186、西农20、丰德存20。高耐旱种质的H₂O₂、MDA含量均显著低于高敏旱种质，CAT活性、Pro含量、SS含量均显著高于高敏旱种质，且CAT活性、Pro含量和SS含量与D值均呈显著或极显著正相关，表明高耐旱种质通过提升CAT活性、积累Pro和SS，降低H_₂O_₂和MDA含量，减轻干旱伤害。

关键词: 小麦, 种质资源, 苗期, 耐旱性, 综合评价, 生理调控