Genetic differentiation between Bruguiera gymnorhiza and B-sexangula in Sri Lanka

The identification of populations of Bruguiera sexangula, Bruguiera gymnorh iza and their putative hybrids in the field is difficult using only morphol ogical and phenological characters. Using a PCR based technique, RAPD (Rand om Amplified Polymorphic DNA), the genetic variation of Bruguiera populatio ns was studied from contrasting climatic and geographic regions along the s outhwest coastal region of Sri Lanka. Out of 45 primers screened, 20 primer s allowed us to observe polymorphism, not only between species (interspecif ic) but also within the species (intraspecific). Analysis of RAPD data appe ars to be helpful in determining the genetic relationship among populations of B. gymnorhiza and B. sexangula. RAPD markers revealed that the two spec ies are well separated without any hybrid position between the two taxa tho ugh they occur in mixed stands. Although sampling sizes of populations of t his study were small, genetic variation among B. gymnorhiza and B. sexangul a populations could be observed. For B. sexangula, it was possible to diffe rentiate each of the three populations, even when using a small number of p rimers.