Genetic diversity of acacia mangium plus tree (superbulk) using est-ssr molecular marker

The application of biotechnology in forest plantation industry is getting more popular over the last decades and many researches have been conducted to develop marker-assisted selection for tree improvement programme in Malaysia. However, to date, marker assisted selection has not yet widely implemented in Sarawak and conventional breeding would take years to select the best characteristics in trees. Thus, this study was conducted to look into the effectiveness in using Expressed Sequenced Tag derived Simple Sequence Repeats (EST-SSRs) marker to estimate the distribution of genotypes and allele polymorphism of Acacia mangium superbulk populations in Sarawak; to determine the relationship or correlation between genetic variation of these populations to environmental and physiological factors and to determine the genetic differentiation of the Acacia mangium superbulk populations in comparison with other Acacia species. In this study, 93 fresh young leaf samples were collected from three different areas, namely Similajau (Borneo Tree Seeds Seedlings Supply Sdn Bhd. (BTSSSB), Bintulu (DAIKEN) and Kota Samarahan (UNIMAS arboretum) and total genomic DNA of the samples were extracted using modified CTAB method. Thirteen EST-SSR markers were chosen to determine the genetic diversity of A. mangium superbulk and fragment analysis was conducted by using ABI PRISM® 3100 Genetic Analyzer and Genemapper™ Version 4.0 software (Applied Biosystems, USA). Statistical analysis performed using PowerMarker software over 13 polymorphic loci revealed that the mean expected heterozygosity or He for the three populations was 0.432 and polymorphic information content (PIC) value of 0.398, respectively. Borneo Tree Seeds Seedlings Supply Sdn. Bhd. population showed the highest level of genetic diversity (N = 40; He = 0.474; PIC = 0.432) compared to Daiken (N = 40; He = 0.458; PIC = 0.429) and UNIMAS Arboretum N = 13; He = 0.364; PIC = 0.333). Mean FST xii ranged from 0.411 to 0.533 which indicates that the surplus of homozygotes generally occur within these populations. This might be due to inbreeding factor or partial selfing in A. mangium superbulk populations and Mean GST value of 0.038 further revealed that a low gene differentiation between all populations (at 3.8%), which signifies that these populations are genetically similar to each other. UPGMA dendogram was also constructed on the A. mangium superbulk populations and it revealed that the three populations belong to the same cluster, with BTSSSB and Daiken populations have the highest similarity coefficient (0.890). Future studies should look into thebreeding patterns in Acacia plus tree populations; the effect of silvicultural regimes in forest plantations to the genetic structure of Acacia species; and the effect of interaction between temporal variations in outcrossing rates with temporal and spatial variations in seedling selection towards genetic structure of Acacia specie