HORTSCIENCE 40(6):1782–1786. 2005. relationships for agronomic crops, fruit trees and ornamental plants, such as Cephalotaxus (Zhang et al., 2000), Dahlia (Debener, 2002), Genetic Relationship of Ornamental daylily (Tomkins et al., 2001), Dendranthema (Zhou and Dai, 2002), Dieffenbachia (Chen Peach Determined Using AFLP et al., 2004), Lagestroemia (Pooler, 2003), Philodendron (Devanand et al., 2004), plum Markers (Goulao et al., 2001), Prunus mume (Ming and Zhang, 2003), and sweet cherry (Struss Dongyan Hu and Zuoshuang Zhang et al., 2001, 2003; Tavaud et al., 2001; Zhou Beijing Botanical Garden, Wofosi Road, Beijing, 100093, China et al., 2002). Previous studies of fruiting peach cultivars Donglin Zhang1 (Aranzana et al., 2001, 2003; Dirlewanger et Landscape Horticulture, Department of Plant, Soil and Environmental Sciences, al., 1998; Manubens et al., 1999; Shimada et University of Maine, Orono, ME 04469-5722 al., 1998) have shown that AFLP technique produces a high degree of polymorphic mark- Qixiang Zhang ers per assay, which could provide an effi cient College of Landscape Horticulture, Beijing Forestry University, Beijing, system for detection and analysis of fruiting peach cultivars. 100083, China In this study, therefore, AFLP was applied Jianhua Li to estimate genetic relationships of ornamental peach taxa, providing insights into their clas- Arnold Arboretum of Harvard University, 125 Arborway, Jamaica Plain, sifi cation and further breeding. MA 02130 Additional index words. breeding, conservation, cultivar, DNA, identification. Materials and Methods Abstract. Ornamental peach (Prunus persica (L.) Batsch) is a popular plant for urban Plant materials. Fifty-one ornamental landscapes and gardens. However, the genetic relationship among ornamental peach peach taxa, which originated from P. persica cultivars is unclear. In this report, a group of 51 ornamental peach taxa, originated from and P. davidiana, were used in this study. They P. persica and P. davidiana (Carr.) Franch., has been studied using AFLPs. The samples were collected from the following botani- were collected from China, Japan, and US. A total of 275 useful markers ranging in size cal gardens and arboreta: Beijing Botanical from 75 to 500 base pairs were generated using six EcoRI/MseI AFLP primer pairs. Garden, Beijing, China (BBG), National Among them, 265 bands were polymorphic. Total markers for each taxon ranged from Institute of Fruit Tree Science, Tsukuba, Japan 90 to 140 with an average of 120. Two clades were apparent on the PAUP–UPGMA tree (JAPAN), and the JC Raulston Arboretum with P. davidiana forming an outgroup to P. persica, indicates that P. davidiana contrib- at North Carolina State University, Raleigh, uted less to the ornamental peach gene pools. Within P. persica clade, 18 out of 20 upright North Carolina, USA (JCRA) (Table 1). The ornamental peach cultivars formed a clade, which indicated that cultivars with upright relationships among these cultivars were growth habit had close genetic relationship. Five dwarf cultivars were grouped to one described by Hu et al. (2003) based on their clade, supported by 81% bootstrap value, indicating that they probably derived from morphological features. a common gene pool. These results demonstrated that AFLP markers are powerful for DNA extraction. Total genomic DNA determining genetic relationships in ornamental peach. The genetic relationships among was isolated from silica gel dried leaves us- ornamental cultivars established in this study could be useful in ornamental peach iden- ing a DNeasy Plant Mini Kit (Qiagen Inc., tifi cation, conservation, and breeding. Chatsworth, Calif.) and following the manu- facturer’s protocols. DNA concentration was Prunus persica (L.) Batsch (ornamental mental features and many new cultivars have quantifi ed using an Eppendorf BioPhotometer peach) is a small deciduous tree of Rose Family been introduced in the nursery trades. However, (Brinkmann Instruments, Inc., Westbury, N.Y.). (Rosaceae). The plant has glabrous branchlets, ornamental peach nomenclature and classifi - All DNA samples were diluted or concentrated serrulate leaves, and subsessile fl owers bloom- cation in the literature are contradictory and to a uniform concentration of 80 µg/mL for the ing before the unfolded leaves during the early confusing. Some ornamental peach cultivars following AFLP procedures. spring. The showy fl owers range from pink to have the same name in the literature, but do AFLP procedure. Amplified fragment red, white, bicolor or tricolor. Growth habits not have the similar morphological descriptions length polymorphism restriction, ligation, range from upright, dwarf, weeping, to fastigi- (Krussmann, 1986; Moore et al., 1993). Others and preselective amplifi cation reactions were ate. Leaf colors vary from green to purple (Hu have different names, but share identical mor- conducted according to the Perkin Elmer et al., 2003). All these characteristics make the phological characteristics (Jacobson, 1996). It AFLP Plant Mapping Protocol (PE Applied ornamental peach an excellent plant for urban is diffi cult to classify ornamental peach taxa Biosystems, Foster City, Calif.) with some landscapes and gardens. based only on morphological characteristics modifi cations suggested by Zhang et al. (2000) Ornamental peach had been cultivated in (Dirr, 1998). Modern technology can aid in except for using MseI adaptor sequence plus China for thousands of years before it was clarifying nomenclature, and in determining CAT, CTC combining with EcoRI adaptor introduced to western countries about three genetic relationships. sequence plus ACT, ACC, and AGG.. Amplifi - hundred years ago (Everett, 1967). Today it is Amplifi ed fragment-length polymorphism cations were electrophoresed at 3000 V and 50 grown in Asia, Europe, North America, South (AFLP) has become a popular marker tech- °C for 2.5 h on an automated DNA Sequencer Africa, and Australia for its outstanding orna- nique in plant genetics because it combines (model ABI 377; PE, Applied Biosystems). To restriction digestion and amplifi cation of DNA avoid contamination from adjacent samples, Received for publication 3 Apr. 2005. Accepted fragments, with no prior knowledge about the odd numbered lanes were fi rst loaded, then for publication 28 May 2005. Maine Agricultural the target genome required (Vos et al., 1995). the even numbered lanes were loaded after and Forestry Experiment Station Publication 2812. We thank Todd Lasseigne, JC Rauslton Arboretum Abundant polymorphisms and reproducibility about one-minute run. at North Carolina State University, and Masami have been proved to be the advantages of AFLP AFLP data analysis. For each primer combi- Yamaguchi, National Institute of Fruit Tree Science technique (Pejic et al., 1998; Powell et al., 1996; nation, the amplifi ed fragments were analyzed of Japan, for providing plant materials. Russell et al., 1997). AFLP markers have been using GeneScan software (version 3.1. Perkin- 1To whom reprint requests should be addressed; extensively and successfully used on detect- Elmer, Applied Biosystems) equipped with ABI e-mail [email protected]. ing genetic diversity and analyzing cultivars 377. The presence and absence of a specifi c 1782 HORTSCIENCE VOL. 40(6) OCTOBER 2005 OOctober.indbctober.indb 11782782 88/11/05/11/05 99:05:43:05:43 AAMM marker were scored as 1 and 0, respectively, using six EcoRI/MseI AFLP primer combina- cultivars of P. persica (CP) (Fig. 1). Prunus for each sample, generating a data matrix. The tions of 51 ornamental peach taxa. Among davidiana formed an outgroup to P. persica, data set was then imported to PAUP (PAUP 4.0, them, 256 markers were polymorphic. The which indicates that P. davidiana is geneti- Swofford, 2002). Pairwise distance compari- number of markers for each taxon ranged from cally distant from other ornamental peach taxa sons were calculated and phenetic trees were 90 to 140 (mean =120, Table 2). derived from P. persica. The clade davidiana constructed using the unweighted pair group Based on 275 useful AFLP markers, genetic (CD) had three taxa derived from P. davidiana method with arithmetic average (UPGMA) in distances among the cultivars were found to be (P. davidiana var. alba, P. davidiana var. rubra, PAUP. Conversion to genetic distance Dxy, was ranged from 0.044 to 0.404 (data not presented). and P. davidiana ‘BBG1’) and supported by obtained by the following equation: Dxy = 1- Sxy The greatest distance (0.404) was between P. 100% bootstrap value. The genetic distance (data not presented)[Sxy = 2Nxy/(Nx+Ny)], where davidiana ‘BBG1’ and P. persica ‘Clarisse’, within these three taxa is 0.16, while the aver- Sxy is the genetic similarity between cultivar x ‘Zhu Fen Chui Zhi’, ‘Genpaishidare’, and age distance of these three taxa to all other taxa and y; Nxy is the number of bands shared between ‘Corinthian White’, respectively. This result originated from P. persica is 0.339. Obviously, cultivar x and y; and Nx and Ny were the number was not surprising given that genetic distances these three taxa are closely related to each other of bands for cultivar x and y, respectively. among the cultivars derived from different spe- compared with ornamental peach taxa derived cies are expected to be higher than those among from P. persica. Prunus davidiana ‘BBG1’, Results and Discussion the cultivars selected within a species. a new cultivar selected by Beijing Botanical Two major clades were recognized in Garden (manuscript in preparation), has upright In total,