本研究利用分布频率、变异系数、Shannon-weaver多样性指数、方差分析及聚类分析对“国家果树种质兴城梨、苹果圃”内保存的梨11个种456份梨资源和种间杂交品种114份共570份材料的39个果实表型性状进行多样性和性状差异的分析，通过相关性、主成分以及回归分析对梨种质资源进行综合评价指标筛选。主要结果如下: 梨种质果实28个字符型性状中检测到132种变异类型，多样性丰富；果实形状、萼片姿态、果肉类型、萼片状态、果锈位置、萼洼状态、风味和果实底色的多样性指数较高，分别为1.949、1.908、1.700、1.681、1.658、1.644、1.610和1.592。梨种质果实11个数值型性状中可滴定酸含量变异系数最高达128.43%，更能体现梨种质间的差异。梨5个栽培种（白梨、砂梨、秋子梨、新疆梨和西洋梨）种群间表型分化系数Vst（66.4%）高于种群内表型分化系数Vst（33.6%），种群间的变异是梨果实性状主要变异来源。系统聚类分析将包括川梨的6个栽培种389份资源分为6大类，组内具有一定的特征，组间存在差异，但并未完全按地域聚类，日韩砂梨和原产中国的砂梨聚在一起；白梨多数与砂梨聚在一起，少数与秋子梨聚在一起；秋子梨和西洋梨分别单独聚类；新疆梨和川梨均未单独聚类。采用主成分分析法和逐步回归分析法从39个性状中筛选出17个性状，决定总变异的99.3%，其中描述单果质量和可食率的性状3个（果实横径、果实纵径和果心大小）、形态特征和外观品质性状5个（果面盖色、果锈数量、果点明显程度、果实形状和果梗长度）和内在品质性状9个（果肉颜色、汁液、香气、风味、果肉质地、果肉类型、可溶性固形物含量、可滴定酸含量和内质综合评价），可作为梨种质资源综合评价指标。

Germplasm resources are an important basis for genetic breeding and analysis of complex traits, and research on genetic diversity is conducive to the exploration and creation of new types of germplasm.  In this study, the distribution frequency, coefficient of variation, Shannon–Wiener index, and variance and cluster analyses were used to analyze the diversity and trait differences of 39 fruit phenotypic traits from 570 pear accessions, which included 456 pear accessions from 11 species and 114 interspecific hybrid cultivars that had been stored in the National Germplasm Repository of Apple and Pear (Xingcheng, China).  The comprehensive evaluation indices were screened by correlation, principal component and regression analyses.  A total of 132 variant types were detected in 28 categorical traits of pear germplasm fruit, which indicate a rich diversity.  The diversity indices in decreasing order were: fruit shape (1.949), attitude of calyx (1.908), flesh texture type (1.700), persistency of calyx (1.681), russet location (1.658), relief of area around eye basin (1.644), flavor (1.610) and ground color (1.592).  The coefficient of variation of titratable acidity in the 11 numerical traits of pear germplasm fruit was as high as 128.43%, which could more effectively reflect the differences between pear accessions.  The phenotypic differentiation coefficient V_st (66.4%) among the five cultivated pear species, including Pyrus bretschneideri (White Pear), P. pyrifolia (Sand Pear), P. ussuriensis (Ussurian Pear), P. sinkiangensis (Xinjiang Pear), and P. communis (European Pear), was higher than the within population phenotypic differentiation coefficient V_st (33.6%).  The variation among populations was the main source of variation in pear fruit traits.  A hierarchical cluster analysis divided the 389 accessions of six cultivated pear species, including P. pashia (Himalayan Pear), into six categories.  There were certain characteristics within the populations, and the differences between populations were not completely clustered by region.  For example, Sand Pear cultivars from Japan and the Korean Peninsula clustered together with those from China.  Most of the White Pear cultivars clustered with the Sand Pear, and a few clustered with the Ussurian Pear cultivars.  The Ussurian Pear and European Pear cultivars clustered separately.  The Xinjiang Pear and Himalayan Pear did not cluster together, and neither did the cultivars.  Seventeen traits, three describing fruit weight and edible rate (fruit diameter, fruit length and fruit core size), five describing outer quality and morphological characteristics (over color, amount of russeting, dot obviousness, fruit shape, and stalk length), and nine describing inner quality (flesh color, juiciness of flesh, aroma, flavor, flesh texture, flesh texture type, soluble solid contents, titratable acidity, and eating quality) were selected from the 39 traits by principal component and stepwise regression analyses.  These 17 traits could reflect 99.3% of the total variation and can be used as a comprehensive evaluation index for pear germplasm resources.