Abstract: The orthogonal design was used to optimize RAPD amplification system of Larix gmelnii(Rupr.) Rupr with five factors (Taq polymerase, Mg²⁺, dNTP, primer, DNA templet) at four levels, respectively. Through the deep analysis, a suitable RAPD-PCR reaction system was established, namely 20 μL reaction system containing 1.0 U Taq DNA polymerase, 2.5 mmol·L^-1 Mg²⁺，0.25 mmol·L^-1 dNTP, 0.5 μmol·L^-1 primer, 1×PCR buffer, 90 ng DNA template. 20 primers with stable amplification and rich polymorphism for RAPD were screened. The optimal annealing temperature for RAPD-PCR reaction was proposed by gradient PCR. The result provided a standardizing RAPD-PCR program for the analysis of genetic diversity of L. gmelnii(Rupr.) Rupr.

Key words: Larix gmelnii(Rupr.)Rupr, RAPD-PCR, orthogonal design, reaction system