Genetic structure of East Asian cultivated pears (Pyrus spp.) and their reclassification in accordance with the nomenclature of cultivated plants

By use of Bayesian statistical inference and allelic data for 18 microsatellite loci, we analyzed the genetic structure of Chinese, Korean, and Japanese pear cultivars and of native populations of Pyrus ussuriensis. Although Japanese pear cultivars had a simple genetic structure, Chinese and Korean pear cultivars were admixures of Japanese pear and native P. ussuriensis from the Asian continent. Genetic differentiation between groups of native populations and those of cultivars was high, but cultivars were not well differentiated from each other. Chinese and Korean cultivars, which have traditionally been classified as either P. ussuriensis, P. bretschneideri, or P. pyrifolia, were much closer to Japanese cultivars, which have traditionally been classified as P. pyrifolia, than to native P. ussuriensis. We propose a new classification of cultivars by using the Group concept in accordance with the International Nomenclature for Cultivated Plants, namely, the Pyrus Ussurian pear group, the Pyrus Chinese white pear group, the Pyrus Chinese sand pear group, and the Pyrus Japanese pear group.