Analysis of leaf morphological diversity of pear (Pyrus L.) preserved in China

Twelve leaf characters (leaf length, leaf width, leaf shape, petiole length, shape of leaf base, shape of leaf apex, leaf margin, seta on leaf margin, status of leaf surface, presence of stipules, colour of young leaf, latitude of leaf in relation to shoot) in 548 Pyrus accessions were investigated in order to reveal the diversity and discuss the taxonomic relationship. There was an abundant diversity in leaf characters of pear. The ovate leaf shape, wide wedge-shaped leaf base, sharp-acute leaf apex, serrate on leaf margin with seta, enclasped status of leaf surface, downward latitude of leaf in relation to shoot, and reddish-green young leaf were abundant, accounting for 90.33, 58.03, 66.97, 81.57, 87.23, 59.27, 86.68, and 35.40%, respectively. The average leaf length, leaf width, and petiole length are 10.8, 7.0, and 4.3 cm, respectively, and the average coefficients of variation were 17.25, 19.04, and 21.06%, respectively. The genetic diversity of colour of young leaf and shape of leaf base were higher than other traits. The variation in pear germplasm resources based on leaf traits among populations was higher than within populations. For almost all of P. bretschneideri, P. ussuriensis, and P. pyrifolia accessions, the leaf shape is ovate, as for the P. communis accessions, 71.4% are elliptic. For 94.3% of the P. bretschneideri, P. ussuriensis, and P. pyrifolia accessions, the leaf margin is serrate, as for P. communis accessions, the crenate, circular, serrate, and entire margin account for 39.7, 34.9, 15.9, and 9.5%, respectively. The seta on margin is present in all of the P. ussuriensis and P. pyrifolia accessions, while in 93.7% of P. communis accessions it is absent. The taxonomic relationship of pears based on leaf morphological characters is also discussed in this paper.