Cinnamomum porrectum (Roxb.) Kosterm., local name Thep tharo, is a rare medicinal and aromatic tree mostly distributed throughout southern Thailand. Inter simple sequence repeat (ISSR) markers were used to analyze genetic diversity of 6 populations, including Phangnga, Phuket, Phatthalung, Satun, Krabi, and Songkhla Provinces. A total of 73 amplified bands were obtained from 117 individuals of all sampled populations using 7 primers. At species level, the percentage of polymorphic loci (P), the mean expected heterozygosity (He), and Shannon’s information index of diversity (I) were high (87.67 %, 0.2883, and 0.4343, respectively). However, P, He, and I were relatively low at population level with the average of 47.03 %, 0.1689, and 0.2508, respectively. Genetic differentiation among populations (Gst) was 0.3551 and gene flow (Nm) was 0.9081. At population level, Songkhla and Phangnga populations showed higher genetic diversity than Phuket, Phatthalung, Satun, and Krabi populations. UPGMA cluster analysis divided the populations into two main groups. Phuket and Krabi populations formed one group. Satun, Songkhla, Phangnga, and Phatthalung populations were in the other groups. Based on the result of this study, it could be suggested that in situ gene conservation is very important for this species, especially as Songkhla and Phangnga populations due their higher genetic diversity and larger population size. At the same time, ex situ gene conservation should be carried out as an option to conserve the genetic material from Satun, Phatthalung, Phuket, and Krabi populations that showed low genetic diversity with small population size and threatened by extinction.
Keywords: Cinnamomum porrectum, genetic diversity, ISSR