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Pasak bumi (Eurycoma longifolia Jack) is a shrubs growing wildly in the forests of Southeast Asia and widely used throughout the region because of its medicinal properties. Uncontrolled harvesting of wild-grown trees has led to rapid decrease of it natural populations, as well as causing a potential decrease in genetic diversity. Information about population genetic of pasak bumi still not determined yet, including the optimal DNA isolation and it reference marker. Therefore, our research was conducted to get information about optimal DNA isolation using CTAB methods and reference marker for population genetic study. DNA isolation was conducted through CTAB (Cetyl Trimetyl Ammonium Bromide) method. The yield DNA was PCR amplified using four barcoding standard marker those were ITS, matK, rbcL and trnL-trnF. The result showed that CTAB method was able to yield good quality DNA and 30% dilution produced the best band. The trnL-trnF primer was able to amplified DNA of pasak bumi with 50∘C annealing temperature, rbcL with 55∘C annealing temperature and ITS with 50∘C annealing temperature. While the matK primer failed to amplified. Keywords: DNA, genetic, isolation, amplification, pasak bumi

The rhizosphere defined as zone surrounds the root that it physical, chemical, and biological character directly influenced by root activities. The rhizosphere is characterized by high microbiological activities compared to bulk soil and affected the plant performance. The objectives of this research were to determine soil respiration and total population of soil microbes, including fungi and bacteria, phosphate solubilizing microbes, and organic matter decomposer microbes. Soil samples were collected from rhizosphere zone (0-20 cm) of kemenyan bunga, kemenyan durame, kemenyan batak and kemenyan minyak in Pardomuan village, Sitellu Urang Julu-Pakpak Bharat, North Sumatera. Microbial population was calculated using plate count method and soil respiration measured using jar methods. The result showed that the highest fungi and bacterial population were found under kemenyan durame rhizosphere those were 13.4 x 107 and 15.7 x107 CFU mL−1. The highest phosphate solubilizing microbes population (96.8 x104 CFU mL−1) was also found in kemenyan jurame rhizosphere. The highest organic matter decomposer microbe found in kemenyan minyak rhizosphere those were 25.1 x104 (fungi) and 73.2 x 104 CFU mL−1 (bacteria). The highest respiration (3.23 mg CO2 100 g−1 day−1) was also found in kemenyan jurame rhizosphere. Keywords: bacteria, fungi, kemenyan, respiration, rhizosphere