Genetic relationships of pear cultivars in Xinjiang, China, as measured by RAPD markers

SummaryThirteen native pear species have been identified in China, of which P. armeniacaefolia Yu and P. sinkiangensis Yu are specific to Xinjiang. P. armeniacaefolia grows wild and a few cultivars have been assigned to this species. Cultivars of P. sinkiangensis have been suspected to be of hybrid origin involving P. communis L. and P. bretschneideri Rehd. In this study, traditional pear cultivars in Xinjiang were evaluated using RAPD markers and compared with representatives of Occidental pear species, cultivars of P. communis and East Asian pear accessions. The combination of 72 pear accessions and 20 selected primers produced 231 scorable polymorphic RAPD bands, of which some were specific to certain species. Five main groups of pear accessions could be distinguished from UPGMA analysis: 1) P. xerophila Yu, its relatives and one cultivar of P. ussuriensis Max., 2) cultivars of P. sinkiangensis, 3) cultivars of P. pyrifolia Nakai and P. bretschneideri, 4) wild Occidental species, cultivars of P. communis and P. armeniacaefolia, and 5) hybrids between P. communis and Chinese or Japanese pear cultivars. The result of PCA generally agrees with that based on UPGMA. Based on RAPD data, some cultivars traditionally classified as P. bretschneideri should be assigned to P. sinkiangensis. Some heirloom cultivars assigned to P. communis were found to be of hybrid origin involving the Chinese white pear (P. bretschneideri) or sand pear (P. pyrifolia). Our results confirmed that P. sinkiangensis is of hybrid origin and at least P. communis, P. armeniacaefolia and Chinese white pears or sand pears have been involved. A further study is needed to understand how pear species and cultivars in Xinjiang are related to those originated from countries in Central Asia.