Abstract: Community structure and diversity of microorganism in bare soil and continuous cropping
protected tomato field were studied with PCR-DGGE technology. Results showed that soil indigenous
bacterial community structure was significantly influenced by planting tomato under protected field，but
soil bacterial community structure and diversity were not sensitive to continuous cropping years.
Compared with soil indigenous bacteria，indigenous fungal community structure was more steady，but the
dominant fungi were more different in the fields with different continuous cropping years，continuous
cropping significantly decreased the number of some fungi，meanwhile，the number of some other fungi
was significantly increased，most dominant fungi populations were enriched in soil with tomato continuous
cropping years of 20，and which number was quite different with the non-dominant fungi populations. The
256 园 艺 学 报 40 卷
change of soil fungi population balance that caused by tomato continuous cropping maybe one of the
important reasons for the tomato continuous cropping obstacle. Recycling and sequence analysis of
prominent electrophoretic bands showed that the dominant bacteria of soil sample belong to Clostridium
butyricum，Uncultured bacterium，Bacillus and Arthrobacter，while the dominant fungus belong to
Saccobolus dilutellus，Uncultured fungus，Lasiobolus ciliatus，Spooneromyces laeticolor and Lasiobolidium
orbiculoides.

Key words: tomato, long-term continuous cropping, soil microbial, PCR-DGGE, community
structure, diversity