Abstract: 【Objective】The study on the diversity and variation of current-year twig and leaf phenotypic traits of pear germplasm resources was conducted in order to provide valuable basic data and theory foundation for normalization, standardization, preservation and construction of pear core collections, and to promote the efficient utilization of pear germplasm resources.【Method】Data were collected for 23 phenotypic parameters of current-year twig and leaf from 548 accessions of 13 Pyrus species preserved in National Germplasm Repository of Apple and Pear according to the method described in Descriptors and Data Standard for Pear (Pyrus spp.) methods. The distribution frequency, coefficient of variation, Simpson index, Shannon-weaver index, correlation and principal component analysis of pear current-year twig and leaf were analyzed using the SPSS19.0 software, and the intraspecific and interspecific genetic diversities of pear were also analyzed and compared. The frequency distributions of quantitative characters were analyzed by Origin 8.0. The crisp-fleshed and soft-fleshed pears were clustered using MEGA 5.0, respectively, according to morphological data.【Result】Analyzing of 15 character traits of pear leaf phenotype showed that 8 out of 15 traits were abundant, namely, ovate shape, wide wedge-shaped base, sharp-acuate apex, serrate on leaf margin with seta, enclasped status of leaf surface, downward latitude of leaf and redish-green young leaf, which accounted for 90.51%, 58.03%, 66.97%, 81.93%, 87.23%, 59.27%, 86.68% and 35.04%, respectively. Regarding the phenotype of current-year twig, which was ample among yellow brown, rich in lenticels, leaf bud slightly held out, obtuse leaf bud apex, size of bud support medium, pubescence on flower bud absent, which accounted for 87.23%, 78.28%, 87.96%, 83.76%, 73.91% and 99.27%, respectively. The Shannon indexes of the color of young leaf and leaf base shape were found to be as high as 2.197 and 1.597, respectively. The analyses of 8 numeric traits indicated that the average coefficient of variation of leaf length, leaf width, petiole length, current-year twig length, twig thickness, internode length, length of flower bud and thickness of flower bud was 17.25%, 19.04%, 20.06%, 23.70%, 15.08%, 19.33%, 20.62% and 16.66%, respectively. Reference cultivars and 5 groups of each trait were proposed based on the statistical analysis of frequency distribution of numeric traits of current-year twig and leaf. Eight numeric traits, including current-year twig, length of flower bud, leaf width and petiole length, were put forward as comprehensive assessment indexes according to the results of correlation and principal component analyses. There were significant differences in 8 pear numeric traits of current-year twig and leaf among and within populations, while phenotypic differentiation coefficient (VST) of intraspecies and interspecies were 41.10% and 58.90%, respectively. Cluster analysis showed that 233 crisp-fleshed local pear cultivars could be divided into 12 categories and 87 soft-fleshed P. ussuriensis accessions into 6 categories. It was worth mentioning that pear resources which was from southwest China were found in most of the groups.【Conclusion】There were abundant genetic diversity based on the phenotype of current-year twig and leaf of pear. The diversities of character traits of color of young leaf and shape of leaf base were higher than the others. The variation coefficients of numeric traits of current-year twig and length of flower bud were also more obvious than the others. These 4 traits can therefore reflect the differences among pear varieties. The variation in pear germplasm resources based on twig and leaf phenotype traits among populations was higher than within populations, suggesting that the variation among populations was the main variation source. Finally, 5 numeric traits were selected to be as the important comprehensive evaluation indexes used for pear germplasm resources.

Key words: pear, germplasm resources, twig, leaf, phenotypic trait, diversity