Genetic Relationships of Pyrus Species and Cultivars Native to East Asia Revealed by Randomly Amplified Polymorphic DNA Markers

Abstract

<jats:p>A total of 118 <jats:italic>Pyrus</jats:italic> sp. (pear) and cultivars native mainly to east Asia were subjected to randomly amplified polymorphic DNA (RAPD) analysis to evaluate genetic variation and relationships among the accessions. Two hundred fifty RAPD markers were scored from 20 decamer primers. RAPD markers specific to species were identified. Clustering analysis revealed two divisions: one comprising cultivars of <jats:italic>P. communis</jats:italic> L., and the other including all accessions of <jats:italic>Pyrus</jats:italic> native to east Asia. The grouping of the species and cultivars by RAPD data largely agrees with morphological pear taxonomy. However, some noted incongruence existed between two classification methods. <jats:italic>Pyrus calleryana</jats:italic> Dcne. clustered together with <jats:italic>P. koehnei</jats:italic> Schneid.<jats:italic>, P. fauriei</jats:italic> Schneid. and <jats:italic>P. dimorphophylla</jats:italic> Makino. <jats:italic>Pyrus betulaefolia</jats:italic> Bge. clustered with <jats:italic>P.</jats:italic> ×<jats:italic>hopeiensis</jats:italic> Yu and <jats:italic>P.</jats:italic> ×<jats:italic>phaeocarpa</jats:italic> Rehd. A noncultivated clone of <jats:italic>P. aromatica</jats:italic> Kikuchi et Nakai grouped with <jats:italic>P. aromatica</jats:italic> cultivars. <jats:italic>Pyrus hondoensis</jats:italic> Nakai et Kikuchi and cultivars of <jats:italic>P. ussuriensis</jats:italic> Max. formed a single group. Some accessions from Korea (named Korean pear) had species-specific RAPD markers and comprised an independent group. Most of the Chinese white pears clustered together with most of the Chinese sand pears. Based on the present results, the new nomenclature <jats:italic>P. pyrifolia</jats:italic> var. <jats:italic>sinensis</jats:italic> (Lindley) Teng et Tanabe for Chinese white pear was suggested. Most accessions of Japanese pears fell into one main group, whereas pear cultivars from Kochi Prefecture of Japan subclustered with some Chinese sand pears and one accession from Korea. Our results infer that some local Japanese pear cultivar populations may have been derived from cultivars native to Kochi Prefecture in Shikoku region, and that the latter may have been introduced from ancient China and/or Korea.</jats:p>

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

“…In the dendrogram of Teng et al (2002), Chinese and Japanese pears were clearly separated, whereas Chinese white pears (traditionally referred to as P. bretschneideri) and Chinese sand pears (traditionally P. pyrifolia) were admixed in the clusters. Ussurian pears were not blended into Chinese white pears in their dendrogram, but this might have been because of the paucity of samples (only three cultivars).…”

“…Iketani et al (1998) pointed out the problem of nativeness and hybridization in classification of the East Asian pear and noted that pure native plants unaffected by hybridization, and large population samples, would be necessary for resolving these issues. Later, Teng et al (2002) and Bao et al (2007Bao et al ( , 2008 analyzed the relationships among East Asian pear cultivars by using molecular markers. However, because most of their materials were cultivated plants, and their data were analyzed by use of phenetics, their results should be evaluated with caution.…”

Genetic diversity and similarity of pear (Pyrus L.) cultivars native to East Asia revealed by SSR (simple sequence repeat) markers

“…A new nomenclature for Chinese white pears have been proposed: P. pyrifolia var. sinensis (Lindley) Y. Teng et K. Tanabe (Teng et al 2002). Other studies using different genetic markers such as isoenzyme (Lin and Shen 1983) and AFLP (Lin et al 2002) with a limited numbers of Chinese pear samples have also inferred the close affinity between Chinese sand pear and Chinese white pear.…”

“…Several different types of DNA markers have been successfully applied for Pyrus cultivar identification and the analysis of genetic relationships (Botta et al 1998;Iketani et al 1998;Kim et al 2000;Kimura et al 2003;Oliveira et al 1999;Teramoto et al 1994;Teng et al 2001Teng et al , 2002.…”

“…Our previously detailed studies with RAPD markers have revealed that P. pyrifolia might be a common progenitor of Chinese sand pears, Chinese white pears and Japanese pears (Teng et al 2001(Teng et al , 2002. A new nomenclature for Chinese white pears have been proposed: P. pyrifolia var.…”