Genetic Relationships among Pyrus pyrifolia Cultivars from Southeastern China and Japan

A total of 90 Pyrus pyrifolia cultivars from southeastern China and Japan were used to assess genetic diversity and overall similarity using eight Amplified Fragment Length Polymorphism (AFLP) primer combinations. Eighty-eight percent of the 429 bands produced were polymorphic. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) cluster analysis of these data support two major groups, mostly consistent with their geographic distribution. Most of the P. pyrifolia cultivars from southeastern China formed one group and most of the Japanese cultivars were in the other group. However, some cultivars from southeastern China and Japan clustered together. These results support our previous studies which indicated that some Japanese pear cultivars are genetically similar to those from Zhejiang and Fujian Provinces of China. Nevertheless, most Japanese pears are genetically distant from Chinese sand pears. INTRODUCTION The genus Pyrus L. (pears), has 22 species according to Challice and Westwood (1973). Pyrus pyrifolia (sand pear) is one of most important commercial pear species in China. Prior randomly amplified polymorphic DNA (RAPD) results showed that P. pyrifolia accessions from Kochi Prefecture of Japan have a high genetic similarity with some Chinese sand pears and the former might originate from ancient China and Korea (Teng et al., 2002). Further, simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) analyses also showed similar results (Bao et al., 2007, 2008). This study estimates the genetic similarity of Chinese sand pears and Japanese pears in more detail by examining more accessions from these two areas than in previous studies. We examined Chinese sand pears from Fujian, Zhejiang and Jiangxi in southeastern China, and Japanese pears from Kochi, Chiba and Niigata using the AFLP technique. MATERIALS AND METHODS DNA Extraction Fresh leaves of 90 P. pyrifolia accessions (Fig. 1) were collected from the China Pear Germplasm Repository in Xingcheng, Liaoning Province (CPGR); from the Chinese Sand Pear Germplasm Repository in Wuhan, Hubei Province; and from Tottori University, Tottori, Japan (TU) and stored at -70°C. Genomic DNA was extracted using the SDS method modified by Teng (2002). Due to the high content of phenol and polysaccharides in pear leaves, genomic DNA was then purified using a purification kit from SBS Genetech Co. Ltd., China. The final DNA concentration was measured by a fluorimeter (DU 800, Beckman, USA) and adjusted to 100 ng/μl. AFLP AFLPs were generated as described by Vos et al. (1995) with modifications outlined by Bao et al. (2008). Primer combinations E-ACT/M-CAA, E-AAC/M-CAG, E-ACA/M-CAG, E-AGG/M-CAA, E-AGG/M-CTT, E-ACG/M-CTC, E-ACA/M-CAA Proc. IS on Molecular Markers in Horticulture Eds.: N.V. Bassil and R. Martin Acta Hort. 859, ISHS 2010 90 and E-AAC/M-CTA were screened over the plant material.