Molecular evidence for the hybrid origin of Bauhinia blakeana (Caesalpinioideae).

Bauhinia blakeana Dunn is the Hong Kong Special Administrative Region emblem and a popular horticultural species in many Asian countries. It was first described as a new species from Hong Kong almost a century ago. This plant is sterile and has long been considered a hybrid, possibly from two related species, B. purpurea and B. variegata. However, not much evidence based on molecular methods was available to support this hypothesis. In this study, sequences of internal transcribed spacer 1 (ITS1), rbcL and atpB-rbcL intergenic spacer for five Bauhinia species and two varieties of one of the species were determined and compared. There were two types of ITS1 sequences in B. blakeana, one indistinguishable from that of B. purpurea and the other one identical to that of B. variegata. This confirmed that B. blakeana was a hybrid of these two species. Chloroplast atpB-rbcL intergenic spacer sequence of B. blakeana was identical to that of B. purpurea, indicating that B. purpurea was the female parent. The hybridization event seemed to occur only recently and was a rare incident. Its occurrence was likely facilitated by interspecific pollen competition. It appeared that human efforts played a crucial role in the preservation and ubiquity of B. blakeana.

DNA methods for identification of Chinese medicinal materials.

As adulterated and substituted Chinese medicinal materials are common in the market, therapeutic effectiveness of such materials cannot be guaranteed. Identification at species-, strain- and locality-levels, therefore, is required for quality assurance/control of Chinese medicine. This review provides an informative introduction to DNA methods for authentication of Chinese medicinal materials. Technical features and examples of the methods based on sequencing, hybridization and polymerase chain reaction (PCR) are described and their suitability for different identification objectives is discussed.

Molecular identification of Astragalus membranaceus at the species and locality levels.

Astragalus membranaceus (Fisch.) Bunge, a commonly used Chinese medicinal material, from certain localities contains more favourable trace elements and fewer harmful trace elements than those from other localities. Therefore, there is a need to distinguish Astragalus membranaceus from different localities. Internal transcribed spacer 1 (ITS1) of the nuclear ribosomal RNA gene of 23 Astragalus membranaceus samples were sequenced to confirm the species of the samples. Arbitrarily primed polymerase chain reaction (APPCR) was then used to obtain unique fingerprints for each sample using several primers. The presence and absence of bands were used for calculating mean similarity indexes among the samples. It was found that the Heilongjiang samples were markedly distinguishable from samples of other localities. In addition, bands common for samples from the same locality were also identified and used to distinguish samples from Neimengu and Shanxi. Therefore, Astragalus membranaceus from these provinces, the major cultivation places in China, can be differentiated.