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.