Genetic variability of Exacum trinervium complex in Sri Lanka

Abstract

Exacum walkeri, E. trinervium, E. axillare and E. trinervium complex including four sub species; E. trinervium, subsp. trinervium, subsp. ritigalensis, subsp. pallidum and subsp. macranthum are medicinal and ornamental plants endemic to Sri Lanka. Taxonomic relationship of these species has been studied based on morphometric, cytological and crossability data. However, this relationship is still a controversy because of different opinions raised from several researches regarding the taxonomy of Exacum trinervium complex. The molecular data have provided more reliable evidences in resolving taxonomic relationship in some plant species. Therefore, in this study the genetic variability of Sri Lankan Exacum trinervium complex species was studied to obtain more refine taxonomic relationship among them. Genetic variability of fifteen individuals from Exacum trinervium complex was studied based on Random Amplified Polymorphic DNA (RAPD) data. Similar banding patterns were observed among subsp. trinervium and subsp. ritigalensis while banding pattern of subsp. pallidum was different from subsp. trinervium and subsp. ritigalensis. The obtained RAPD results combined with the morphological data indicated that subsp. trinervium and subsp. ritigalensis can be considered as one subspecies rather than two. More molecular based studies combined with morphological, anatomical and cytological studies are necessary to clarify this relationship further.