RECONSIDERATION ON THE ORIGIN OF CULTIVATED PEARS NATIVE TO EAST ASIA

The commercial pear cultivars native to East Asia are composed of five groups: Ussurian pear, Chinese white pear, Chinese sand pear, Xinjiang pear, and Japanese pear. It has been well known that Ussurian pear cultivars are derived from Pyrus ussuriensis, Chinese sand pear cultivars from P. pyrifolia grown wild in central and southern China. However, the origin of Chinese white pear cultivars and Japanese pear cultivars, and the genetic makeup of Xinjiang pears are still obscure. Chinese taxonomists have assigned cultivars of Chinese white pears to P. bretschneideri. Researchers outside of China speculated that P. bretschneideri might be a natural hybrid between P. betulifolia and cultivated P. pyrifolia, and Chinese white pear cultivars may originate from hybridisation between P. ussuriensis and P. pyrifolia. By means of RAPD analysis, we found RAPD markers specific to P. betulifolia or P. ussuriensis are not present in Chinese white pear cultivars. On the other hand, Chinese white pear cultivars are most closely related to Chinese sand pears based on analyses of RAPD markers, AFLP markers and SSR markers. A new nomenclature for Chinese white pear cultivars has been proposed: P. pyrifolia var. sinensis. As for the origin of native cultivars of Japanese pears, both our study and other researches using different DNA markers infer that at least some Japanese pear cultivars or their progenitors may have been introduced from ancient China and Korea. Xinjiang pears, mainly distributed in northwestern China, have been suspected to be of hybrid origin involving P. communis and Chinese white pears. However, RAPD analysis indicated that at least P. communis, P. armeniacifolia and Chinese white pears or sand pears have been involved in the origin of Xinjiang pears.