Molecular phylogeny of Dendrobium Callista-Dendrobium complex
2005
Wongsawad, P. | Handa, T. | Yukawa, T.
Within one of the largest orchid genera Dendrobium, sections Dendrobium (ca. 60 species) and Callista (14 species) include many horticulturally important species such as D. nobile, D. anosmum, D. chrysotoxum and D. densiflorum. Although the floral structure of section Dendrobium is identical with that of section Callista, a single character- the reduced leaf sheath-characterizes the latter. To clarify genetic relationships and taxonomic positions of Dendrobium sections Dendrobium and Callista, molecular phylogenetic analyses of the internal transcription spacer (ITS) region of the nuclear ribosomal DNA and the maturase-encoding gene (matK) of the chloroplast genome were conducted. The principal results from this study show that: 1) Phylogenetic trees are highly correlated between ITS and matK analyses. 2) Dendrobium and Callista sections are not monophyletic because several species in section Callista are nested within the clades of section Dendrobium. 3) Section Dendrobium comprises at least 7 clades. 4) Section Callista comprises at least 3 clades. 5) Results from hybridization experiments are generally consistent with phylogenetic relationships inferred from the analyses. The results suggest a neccessity for taxonomic revisions of the complex and offer new directions for breeding programmes.
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