Thailand is a tropical country with very species-rich forests. The genetic resources of many forest species are endangered due to rapid deforestation. Approximately 10 years ago researchers started to use gene markers in Thailand in order to assess genetic structures of important forest plants and to investigate the genetic system of indigenous species.
Isoenzymes are the most frequently used gene markers, but molecular markers are gaining importance as a tool also in Thailand. Genetic variation of Pinus merkusii is low, but other species (Mitragyna burnonis, Azadirachta indica var. siamensis, Cycas siamensis) are much more variable. Results of a genetic inventory in 11 populations of Pinus merkusii are presented. Populations differ clearly with regard to the amount of genetic variation. Remarkably high proportions of selfing was estimated in most of the investigated populations.
Based on the results of the genetic inventory the establishment of ex situ conservation stands is suggested as an important complementary measure to in situ conservation. Marker-assisted population genetic studies do not only improve our understanding of the genetic system of tropical forest species. They also form an important basis for the formulation of sound conservation strategies.