Random amplified polymorphic DNA analysis of Thunbergia laurifolia Lindl. and its related species

Abstract

Thunbergia laurifolia Lindl. is an important herb in Thai folk medicine that has been widely used as an antidote, anti-inflammatory and antipyretic. However, counterfeits of T. laurifoliahave been commonly found in Thai herbal markets and have arisen based on their similarity in appearance and shared common names. Flowers of plants belonging to Thunbergiaspp., including T. laurifolia, Thunbergia grandiflora and Thunbergia erecta, look similar to each other, which often cause confusion when identifying these species. Moreover, there is another group of plants with names that share a similar common Thai name, “Rang Chuet”, which includes a Curcuma sp., Rinorea sp., Crotalaria spectabilis, and T. laurifolia. In this study, we developed a random amplified polymorphic DNA (RAPD) method to facilitate the rapid detection of these medicinal materials. Out of 80 screened primers, nine gave clear and reproducible RAPD patterns. Among 164 amplified bands, 70 bands were polymorphic in six species. The dendrogram was constructed using unweighted pair group method with arithmetic averages (UPGMA), and the genotypes were differentiated into three main groups. The RAPD profiles of six species showed low similarity indices (0.1235 to 0.3137), whereas the genetic relationship was associated with the botanical characterization. These results indicate that RAPD is a useful tool for differentiating T. laurifolia from its related species. Key words: Acanthaceae, DNA fingerprint, molecular characterization, random amplified polymorphic DNA, Thunbergia laurifolia.