Microbial Aspects Of Ginger Continuous Cropping Soil In Qianwei, Sichuan

In this study, we collected four kinds of ginger continuous cropping soil sample, including sick ginger rhizosphere soil (SGRS) and sick ginger non-rhizospheric soil (SGNRS), normal ginger rhizospheric soil (NGRS) and normal ginger non-rhizophere soil(NGNRS) from Zhagu town in Qianwei county, Sichuan Province, and determined the microbial flora quantity by pour plate method, and then measeured the soil catalase activity, urease activity, neutral phosphatase activity, and soil microbial biomass C, N. By using pour plated method, 38 bacterial strains were isolated, and 16S rDNA PCR-RFLP,16S rRNA gene sequence analysis was used to do their genetic diversity and phylogeny. Finally, PCR-DGGE was performed to reveal the soil microbial diversity. The results were as follows:1. The quantity of soil bacteria in SGR increased, but the number of actinomycetes and fungi decreased significantly; however, the quantity of actinomyces in SGNR increased markedly, the fungus and bacteria number did not change obviously.2. In SGRS, the soil neutral phosphatase activity and urease activity decreased, but catalase activity increased, which suggested that, the plant root exudates inhibited urease activity, neutral phosphatase activity, whereas catalase was then promoted because of continuous cropping.3. Analysis of 16S rDNA PCR-RFLP revealed that, at the level of 75% similarity,38 bacteria were divided into 6 genetic groups. The results also showed that the difference and diversity was existed among these strains.4. Based on the results above,13 representative bacterial strains were selected to do 16S rDNA sequence analysis, and the phylogenetic tree was constructed. The results showed that 13 representative strains distributed into six phylogenic branches, including genus Pseudomonas, Acinetobacter, Bacillus, Enterobacter, Sphingobacterium and Lysobacter.5. The results of soil fungus PCR-DGGE analysis suggested that, though the fungus flora between SGNRS and NGNRS was closer than that in SGRS and NGRS, the similarity was not high, which revealed that ginger continuous cropping led to the variation of soil microbial population.