In order to understand phenotypic variation law and diversity characteristics of Leymus racemosus ( Lam.) Tzvel. populations, sixteen phenotypic characters of five populations of L. racemosus distributed in Altai Region of Xinjiang ( which were located in Altai City, Fuhai County, Buerjin County and Habahe County, respectively) were detected. On this basis, Shannon-Weaver index ( H') analysis and principal component analysis of these phenotypic characters were carried out. The results show that there is large difference in sixteen phenotypic characters among the populations, in which, averages of phenotypic characters of two populations distributed in Habahe County are higher. Coefficient of variation of phenotypic characters within populations is 5. 97% -40. 05% with large difference. In which, coefficient of variation of length of the first internode under ear within populations is large with a value of 17. 16%-40. 05%. On the whole, variations of some characters related to vegetative growth ( such as length of the first internode under ear, length and width of flag leaf, etc) within populations are large, while those related to reproduction are small. Among populations, coefficients of variation of length of the first internode under ear, length and width of flag leaf all are large with a value of 31. 85%, 26. 87%and 27. 85%, respectively, while those of lengths of spikelet and outer glume and number of ear pitch all are small with a value of 15. 21%, 16. 53% and 16. 91%, respectively. There is large difference in H'value of sixteen phenotypic characters among five populations, and H' average value of phenotypic characters within populations ( 1 . 660 ) is obviously higher than that among populations ( 0 . 239 ) . The principal component analysis result shows that cumulative contribution rate of the first five principal components is 80. 210%, in which, loads of characters related to vegetative organs ( such as plant height, length of the first internode under ear, length and width of flag leaf, number of node) in the first principal component are large, those of characters related to reproductive organs ( such as length and width of ear, length of outer and inner glumes, length and width of spikelet, length of lemma) in the second to the fourth principal components are large, indicating that the twelve characters are dominant factors of variation of phenotypic characters of L. racemosus population. It is suggested that phenotypic diversity among populations of L. racemosus is lower than that within populations, and phenotypic variation of vegetative organs is dominant factor leading to phenotypic diversity of L. racemosus population.%为了解大赖草种群﹝Leymus racemosus ( Lam.) Tzvel.﹞的表型变异规律及多样性特征，对分布于新疆阿勒泰地区的5个大赖草种群(分别位于阿勒泰市、福海县、布尔津县和哈巴河县)的16个表型性状进行了测定；在此基础上，对各表型性状进行了Shannon-Weaver指数( H＇)分析和主成分分析。结果表明：各种群间的16个表型性状均存在较大差异，其中分布于哈巴河县的2个种群各表型性状的平均值均较高。种群内各表型性状的变异系数为5.97%~40.05%，差异较大；其中，穗下第一节间长度的变异系数在各种群内均较大(17.16%~40.05%)；总体上看，种群内与营养生长有关的性状(如穗下第一节间长度、剑叶长度和宽度等)变异较大，而与繁殖有关的性状变异较小。在种群间，穗下第一节间长度、剑叶长度和宽度的变异系数均较大，分别为31.85%、26.87%和27.85%；而小穗和外颖长度以及穗节数的变异系数均较小，分别为15.21%、16.53%和16.91%。5个种群间16个表型性状的H＇值均有较大差异，并且，种群内各表型性状的H＇平均值(1.660)明显高于种群间(0.239)。主成分分析结果显示：前5个主成分的累计贡献率为80.210%，其中，第1主成分中与营养器官相关的性状(如株高、穗下第一节间长度、剑叶长度和宽度、茎节数)载荷较大，第2至第4主成分中与繁殖器官相关的性状(如穗长度和宽度、外颖和内颖长度、小穗长度和宽度以及外稃长度)载荷较大，表明这12个性状为大赖草种群表型性状变异的主要因子。研究结果显示：大赖草种群间的表型多样性低于种群内，且营养器官的表型变异是导致大赖草种群表型多样性的主要因子。
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