Chimonanthus praecox (L.) Link, wintersweet, belongs to Calycanthaceae. It is a deciduous shrub and blossoms in winter from late November to March. Its flowers are strongly fragrant, with tepals arranged in three layers. Usually, outer tepals are scale-like, and the middle and inner tepals are waxy and translucent. The unique flowering time and long blooming period made it one of most popular ornamental plants in China. Wintersweets were extensively cultivated as garden, potted, and cut-flower plants. Also, it is a traditional Chinese medicinal plant for the treatment of heatstroke, cough, scald, and bruise (Zhao et al., 1993). In recent years, this plant has been brought further attention as a new source of natural essential oil, which can be used in cosmetics, perfumery, and aromatherapy.
The natural distribution areas of wintersweet are west of the Hubei and Hunan provinces, south of Shanxi province, and east of Sichuan and Guizhou provinces in China (Chen and Chen, 1999). The plant has been cultivated for more than 1000 years as an ornamental plant. It was introduced to Korea between 1611 and 1628 (Feng et al., 1990), then to Japan, Europe, America, and Australia.
After a long history of cultivation, a lot of wintersweet cultivars were developed, and many germplasms were collected in Wuhan and Nanjing, China, in recent years. Accurate identification and correct nomenclature of these cultivars are essential for the management of wintersweet germplasm resources. However, only a few cultivars were named, and some cases of homonymy and synonymy exist. The genetic information of wintersweet germplasm is also poorly understood. Although biochemical markers and morphological traits had been used in attempts to understand their genetic diversity (Chen, 1995; Zhao et al., 2004), the validity of the results obtained from such studies is considerably affected by the sensitivity of these traits to environmental factors and physiological stages of plants.
Polymerase chain reaction (PCR)-based DNA marker technologies are useful tools to identify closely related plants and to evaluate the genetic homogeneity of cultivars (Siragusa et al., 2006). Among the various molecular marker techniques, intersimple sequence repeat markers (ISSR) and random amplified polymorphic DNA markers (RAPD) are two commonly used methods, mainly because they are simple to execute, are low cost, and require neither sequence information nor prior genetic studies (Williams et al., 1990; Zietkiewicz et al., 1994). Many recent papers have demonstrated the high potential of these two markers in identification (Belaj et al., 2004), classification (Suo et al., 2005), and diversity analysis (MirAli and Nabulsi, 2003) of germplasm resources in agricultural crops. The objectives of this study were to set up a molecular profile that would allow a precise identification of wintersweet germplasm and to evaluate their genetic diversity and relationship based on these two markers.
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