![]() The marker transferability was tested upon two additional Hopea species, H. chinensis Hand.-Mazz. Based on the assembled contigs, 26 novel microsatellite markers were developed and characterized using 50 individuals of this species, 12 of which were found to be polymorphic. In this study, we sequenced the genome of H. hainanensis using next-generation sequencing technology. Lee et al. ( 2004a) developed SSR markers for Hopea bilitonensis from dinucleotide repeats-enriched genomic library and validated 15 of them across 24 adult trees, and however, they did not investigate the transferability of these SSR primers. Indeed, microsatellite loci have been isolated and characterized for species in genera Shorea, Vatica, Dipterocarpus, Neobalanocarpus, and Dryobalanops (Guo et al., 2017 Isagi et al., 2002 Iwata et al., 2000 Lee et al., 2004b Nanami et al., 2007). However, the development of informative microsatellite markers is first step in population genetic studies. Microsatellite markers are widely used to estimate genetic diversity, fine-scale spatial genetic structure, gene flow, and mating system for endangered species in Dipterocarpaceae (Finger et al., 2012 Lee et al., 2013 de Morais et al., 2015). Population genetic studies focused on dipterocarp species have been carried out for the purpose of conservation and restoration (Finger et al., 2012 Ismail et al., 2014). Understanding the genetic diversity, population structure and mating system of these endangered species is crucial and of priority for the effective management and conservation (Frankham, 1995). The unsustainable exploitation for timber and deforestation for agriculture render many dipterocarp species now being classified as endangered (Ghazoul, 2016). Many species of this family constitute important timber resources and thus have been heavily exploited by local countries in tropical Asia. Trees of this family dominate Southeast Asia's tropical forests, accounting for 20%–50% of forest basal area and often well over 50% of canopy trees (Ashton, 1988 Ghazoul, 2016). Hopea hainanensis belongs to the family Dipterocarpaceae, which comprises 16 genera and more than 500 species (Ashton, 1988). The extracts from stems and barks were reported to have potent antioxidant activities, which could be used as candidates for pharmaceutical products or food additives (Ge et al., 2009). In addition to the highly valued wood, H. hainanensis is rich in bioactive compounds. This species is scarce in its natural habitat and is assessed as endangered according to the IUCN Red List of Threatened Species (Ly et al., 2018). The remaining population of H. hainanensis is severely fragmented and isolated in a few reserves in Hainan Island. As a result, adult trees of this species had been overly logged, leading to a reduction of 50%–70% population in the last three hundred years (Ly et al., 2018). Hopea hainanensis is known for its highly valued timber which is extremely durable and suitable for making boats and building bridges and houses (Li et al., 2007). It is found in tropical lowland forest of Hainan Island and northern Vietnam (Li et al., 2007). Hopea hainanensis Merrill & Chun is a large evergreen tree that can grow up to 20 m. The 12 polymorphic microsatellite markers could be applied to study genetic diversity, population differentiation, mating system, and fine-scale spatial genetic structures of H. hainanensis as well as its close relatives, facilitating the conservation and restoration of these endangered but valuable Hopea species. A neighbor joining dendrogram clustered all individuals into two major groups, one of which was exclusively constituted by H. hainanensis, while the other consisted of two subgroups, corresponding to H. reticulata and H. chinensis, respectively. The results showed that H. reticulata and H. hainanensis had similar levels of genetic diversity. and Hopea reticulata Tardieu, in which 3 and 7 microsatellite markers were found to be polymorphic, separately. Primer transferability was tested with Hopea chinensis Hand.-Mazz. GENODIVE analyses indicated that the number of alleles ranged from 2 to 6 per locus, and the observed and expected heterozygosity varied from 0 to 0.755 and from 0.259 to 0.779, respectively. Twelve markers were found to be polymorphic in H. hainanensis. Twenty-six microsatellite markers were developed based on next-generation sequencing data and were genotyped by capillary electrophoresis on an ABI 3730xl DNA Analyzer. Microsatellite markers were isolated and characterized for Hopea hainanensis Merrill & Chun, an endangered tree species with scattered distribution in Hainan Island and northern Vietnam. ![]()
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