The genus Dendrobium is one of the largest genera in Orchidaceae family, comprising ≈1200 species (http://en.wikipedid.org/wiki/list_of_Dendrobium_species) of Dendrobium distributed in tropical and subtropical Asia and Oceania. They have been used not only in traditional Chinese medicine in Asian countries (Bulpitt et al., 2007), but also in commercial cut flowers and potted plants (Chen and Tsi, 2000). For commercial production of cut flowers and potted plants with new floral characteristics and other beneficial traits, a large number of novel cultivars of Dendrobium have been produced through interspecific hybridization in Japan and Korea. In China, there are 74 native species and two varieties of Dendrobium classified into 12 sections by traditional characteristics, including Grastidium (four species), Callista (six species), Dendrobium (36 species), Distichophyllum (one species), Breviflores (two species), Stuposa (one species), Pedilonum (three species), Formosae (seven species), Stachyobium (five species), Crumenatae (four species), Aporum (three species), and Strongyle (two species) (Tsi et al., 1999). Therefore, these species of Dendrobium should be exploited for breeding.
It is important for breeding to understand the genetic relationships and molecular phylogeny of the genus Dendrobium. In recent years, genetic relationships and molecular identification of Dendrobium species have been measured by different molecular tools, including chloroplast DNA (Yukawa et al., 1993, 1996), internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA and plastid mat K (Burke et al., 2008; Lau et al., 2001; Tsai et al., 2004; Wongsawad et al., 2001; Yuan et al., 2009; Yukawa, 2001), simple sequence repeat (SSR) marker (Gu et al., 2007; Yue et al., 2006), and intersimple sequence repeat (ISSR) marker (Wang et al., 2009). However, much information related to taxonomy and phylogenesis of the Dendrobium genus still needs to be solved. Hence, there is a need to study the genus Dendrobium using more abundant and reliable characters such as AFLP markers. The AFLP analysis provides a powerful DNA fingerprinting technique for DNAs of any origin or complexity, needs no cloning and sequencing, and produces a large number of recordable fragments, which enhance its power to detect polymorphism (Vos et al., 1995). The AFLP technique had been successfully used in the estimation of genetic relationships and differentiation among individuals, populations, and species of a wide range of plant families (e.g., Depypere et al., 2009; Karimi et al., 2009; Pamidiamarri et al., 2009; Seehalak et al., 2006). In particular, the genetic diversity and population structure of D. officinale was identified by AFLP (Li et al., 2008).
In the present study, we collected 37 native species of Dendrobium in China and 63 hybrid cultivars of Dendrobium originated from Japan and Korea. The pedigree of some hybrid cultivars, which was obtained by searching the web (http://apps.rhs.org.uk/horticulturaldatabase/orchidregister/orchidregister.asp), was displayed in Supplemental Figure 1. The main objectives of this research were: 1) to test the AFLP technique for molecular identification of collected Asian Dendrobium; 2) to assess phylogenetic relationships among tested native species and hybrid cultivars of Asian Dendrobium; and 3) to supply molecular evidence for classification of Asian Dendrobium.
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