Abstract: A Polymerase Chain Reaction-Denaturing gradient gel electrophoresis (PCR-DGGE) method was used to determine the rhizosphere microorganism diversity of Syzygium grijsii after different cultivation times. Total community DNA was extracted and purified from soils by an improved Protease K-CTAB method, and then amplified using eubacterial 16S rDNAs primers. The PCR products were analyzed by DGGE to obtain bacterial community patterns. The electrophoresis lanes obtained by PCR-DGGE were legible and distinguishable. The results showed that rhizosphere microorganism diversity could be significantly affected by cultivation time. Soil microorganism diversity increased with cultivation time, with the peak diversity index of 2.741 after 4 years or so, then the diversity index decreased to a lower value of 1.378 after 8 years. Composition of rhizosphere microorganism community had a great difference in different cultivation times. Characteristic of rhizosphere microorganism could be used as a guiding factor for changing flowerpot. For S.grijsii, 4-6 years might be a suitable time to change flowerpot, as rhizosphere microorganism of S.grijsii in this time would have the highest diversity, and would be easy to establish.

Key words: Syzygium grijsii, rhizosphere microorganism diversity, cultivation time, PCR-DGGE analysis